quote:

Originally posted by SmokinJ:
Gear,

I shot those Loverins from that SAKO today. The 4531 gave me an inch group. The SuperPerformance power really opened them up. Interesting because that Performance powder has a slower burner and not so much a peaky pressure curve. I'll tweak that 4831 load and I'll throw another powder into the mix.

Joe

That's a good start on getting along w/o me. I'll be gone for the weekend and will be out of touch. I know that must really upset you as you'll be missing me something terrible........

Given your proven lack of veracity on this thread (most every other thread you been on.....one of the reasons you banned from 2 other forums) ......do you really expect anyone to think 25 yard groups (pages 2 & 6 specifically) impress anyone? Do you think claiming the 5 closest shots (was that also 25 yards? ) and then pasting up all the other holes claiming them as "another load" fools anyone?

Soooooooo, you have a good weekend

Larry Gibson

"I love hearing myself talk and reading my post" Larry Gibson

Larry, the difference between you and some of the rest of us is you need us, but we do not need anything from you.

I'll be out all weekend too.

Gear

Oh me. Everybody gone for week-end. Dallas Cowboys not playing as they already played Wednesday night and beat the defending world champions. What to do?

Maybe you should spend the weekend working on a new routine since your current bit is pretty stale.

Pat I--Giants fan?

Bears...thanks for asking. Still suggest the downtime be spent working on a new act. Maybe something that includes sheep would bring down the house or has that already been done??

Pat, I was on CBA's website and I noticed you're not Region 4 director anymore. Stan Livingston is. What's going on with that?

quote:

Originally posted by Pat I.:
Larry why do you bother arguing with these simple minded dumbass lying assholes. Just let them talk to themselves and eventually they'll dry up and blow away.

Don

Gear,

Well went out with the SAKO again using the 150 Grain Lyman Loverin. I changed the 4831 charge and tried a 4350 load also. The 4831 wasn't acceptable but the 4350 shot a 3/8 group. Shooting 3 shot groups to conserve components. So loaded up more then 3 with the 4350 to see how she holds the group. It's in the velocity range that I told you and really is a sweet load. I believe it would be a really great deer load. I'll let you know how the larger group shooting goes. This is without any special things down to the load except using the RCBS style of expander. Nothing else, stock Rem brass. Seems I don't have to do anything to it.

quote:

Originally posted by SmokinJ:
Pat, I was on CBA's website and I noticed you're not Region 4 director anymore. Stan Livingston is. What's going on with that?

Looking for someone else to snitch to Joe? Do yourself a favor and stay away from the CBA webite. You're not in the same league.

quote:

Originally posted by Pat I.:

quote:

Originally posted by SmokinJ:
Pat, I was on CBA's website and I noticed you're not Region 4 director anymore. Stan Livingston is. What's going on with that?

Looking for someone else to snitch to Joe? Do yourself a favor and stay away from the CBA webite. You're not in the same league.

Apparently you're not either. Tell Gibby I know all about his behind the scene underhanded tactic to pm my friend and try to get him to come over to his camp,which we know is the incorrect rpm threshold bs.

Answer this if you will. Gibby runs 45 2.1 down as much as me, and you do too, so why is Gibson buying 45 2.1's 30 caliber mold? That makes the second one of 45 2.1's designs that I've shot and made perform. Gibson can't buy them fast enough. He doesn't have the cast reloading knowledge to make it work. Neither do you.

I hope Gibby was worth it Pat.

quote:

Tell Gibby I know all about his behind the scene underhanded tactic to pm my friend

I didn't realize 6 feet tall invisible rabbits could receive PMs.

quote:

Originally posted by Pat I.:
Very true my simpler sibbling of the Brothers Grimm but I do realize and recognize when someone is completely FOS.

Kind of like when some know it all's said one would sail off the end of the world because it was flat huh??? That's you and Gibson, can't be taught anything, set in your ways.

See on another forum where more are shooting cast in the AR 15 and some with fast twist barrels. The bullet has to fit the throat and be loaded correctly, and if you want to push it powder choice is critical especially with softer alloys. Don't be afraid of the rpm threshold because it doesn't really apply to the distances we will be shooting cast.

ok guys recess is over. Need my fix. Start your engines and let the games begin.

Ray I believe the game is over. Larry has managed to get three of his friends banned from here. He should be mighty proud of himself.

Speaking of velocity I heard swheeler can get a cork out of whiskey bottle well into 20 fps and that's with a 1 in hand twist too. About the best shooting he does with anything.

quote:

They do, I never "claimed" they didn't. What I said was that over spinning a bullet (cast or jacketed) will cause some degree of inaccuracy. Let's take the .223/5/56 in ARs for example as it is the topic cartridge/rifle of this thread; The 8" twist is the accepted twist for best accuracy at 600 - 1000 yards with 70 - 85 gr bullets right (yes joe, that's what ALL the winning HP shooters use). Why don't they use a 7" twist barrel anymore? Because it was found the 8" twist did not over spin the bullets and gave better accuracy at longer range than the 7" twist. The same bullets also drifted less in the wind with the 8" twist because the BC was higher. Why don't they use the 9" twist? Because that twist does not adequately stabilize (underspins) the bullet and it is not as accurate as the 8" twist. That is with jacketed bullets of course. Every bullet, cast or jacketed, will have an optimal rotational speed (RPM) at which it will give the best accuray.

Keep mind what Mr Gibson said above. Recently a test was done on five rifles with different twists in the same caliber. That's two more then Mr. Gibson old test done on three of his own different rifles. Also remember from above Mr. Gibson said the 8 twist was overall the best. Notice in the chart provided that the faster twists shot the lighter bullets better then the slower twists which should have done better.


The bottom line is that conventional wisdom about the relationship between twist rate and bullet weight/length does generally hold true, but only in general, and not as applies to individual loads in individual bores. For each individual rifle, with any individual rifle, all bets are off, and there's simply no predicting which bullet weight will shoot best in which rifle with which twist rate. Conventional wisdom and rules of thumb are fine, but the only way to really find out what a bullets shoot best in your gun is just to take it out and shoot it---with everything.

Sierra Bullets recommmends a minimum 1:6.5 twist for handloading it's 90 grain MatchKing BTHP. Remember above above Mr. Gibson said the 8 twist was the best at the matches for bullets ranging from 70 to 85 grain bullets. Now do any of you think that since Sierra recommends that minimum 6.5 twist for a 90 bullet that a bullet that weighs 85 grains is going to stabilize well in an 8 twist?

All this holds true to a cast bullet as long as it's balanced, fits the throat correctly, is loaded correctly, enters the bore straight, and exits the muzzle correctly.

The rpm threshold theory is BS.

Joe

That's a lot of stupid erronious conclusions from a test that is totally non relevent to what I said, what you quoted. But then that is so atypical of you; stupid non relevent conclusions.

Larry Gibson

Just as there are lot of stupid erronious conclusions from the stupid test you did with your three rifles in 30 caliber.

Regarding that book you mentioned on Fluid Dynamic if you understand any words but the articles ( "a", "an", and "the") in that paper I would be flabbergasted. I can tell you that the full conversation of mass, momentum, and energy equations governing continuum fluid flow, and that they pertain in the general case of flow involving compressibility, friction, heat, body forces, mass addition, etc. (they are the continuum fluid flow governing equations without simplifying assumptions, as contrasted to the Euler equations, or newtonian flow, etc. ) But you Larry Gibson have a clue about that? Seriously?

Now on a more serious note that book pertains to the generalized case of a fluid in a cylindrical container NOT a cylinder (vaguely bullet-like body) in a free fluid member! They are talking about a paint can (or cylindrical void) full of warmed expanding spinning goo heated on one end, not an ogive bullet flying supersonically through a free medium. How Gibson thinks this has ANYTHING to do with the question of RPM and down range accuracy?

Basically Gibby your rpm threshold theory is BS that you made up.

Of the moulds you have the 311334 is going to be the best choice in the .308W out of the AR10 to push the RPM threshold up. Any elementary cast reloader should have figured that out for an AR10, which Mr. Gibson doesn't own or shoot. It's hindered by the magazine oal 2000+ fps should be entirely feasable with that bullet. If that loaded cartridge feeds well in the AR then the sating depth is about right with the top of the GC remaining in the bottom of the case neck. I suggest starting off with AA4350 or RL19 with 35 gr of either. Work up in 1 gr increments using a minimum of 5 shot groups. One grain increments are pretty damn huge No dacron or other filler is needed. You want to use a slower powder that ignites easily and consistently at lower pressures and gives 2000+ fps with the desired level of useable accuracy ar 80% or greater loading density.

In group testing when you get flyers (not called shots) or the accuracy goes south is when the RPM threshold is crosed. See that's were you fail as a cast bullet reloader and shooter. You automaticaly blame your lousy loading and shooting on the bs rpm threshold. If a load is reached before that which meets the accuracy and fps criteria you can then tweek the load +/- using 10 shot groups for the best load evelopment. If either of those powders don'r work out then try a slower powder such as H4831SC or perhaps RL22. Bottom line is Gibby doesn't know what powder it takes

Once you get a combination that is working above 2000+ fps then you can tweek the bullet with strong and tougher alloys such as badgerdd mentions with the addition of babbit to up the velocity a bit. As 357maximum mentions there is no secret squirrel stuff or decoder rings needed. Paraphrasing yet more people Larry?? Might as well see how far you can push the RPM threshold up with the 311334 before having to get a custom mould. Just might not need a cutom mould to reach your objective with your AR10. That's why you ordered one of 45 2.1's custom designs, HUH?

Larry Gibson

Gibby, everyone is tired of hearing your "benchrester shooters use the slowest twist they can to stable a bullet". There are other reasons too, but you wouldn't know that. You only know what you paraphrase.

You're wrong about the 7 twist isn't the best twist for the .224. Equally wrong that you interpreted those books you read wrong. Maybe you better take a look at this:

: Indeed good advice. One of the raps against 6.5mm cartridges, especially
# : with 140 gr. bullets is that "they don't group" at 100 yds. However, if
# : tested at 200 or 300 yds, the groups, on an M.O.A. basis are *tighter* than
# : at 100 yds. The bullets just needed a little time to "settle down" in their
# : trajectory.
#
# I've heard for many years of these `raps' with just about all bore sizes.
# So some time ago, I did some tests to find out what causes this `wait until
# they settle down [go to sleep is a common expression]' philosophy. When
# bullets were fired at muzzle velocities fast enough to spin them too fast,
# they always grouped smaller in MOA at longer ranges than shorter ranges.
# When fired just fast enough to spin at the lower end of their required RPM
# range, groups were equal in MOA through 300 yards or thereabouts. Groups
# did enlarge due to velocity spread and time of flight which is what the
# laws of physics predict.

I read a similar account in Handloader recently where the author tried
to answer a question about overstabilization. He mentioned how complicated
it was and then proceeded with the bullet going to sleep story. I still
couldn't figure it out. The bullet should become more stable due to the
decreased drag down range, and the bullet is more stable if spun faster
initially, so what makes it group poorly at short range? It sounds
like the story is that an overstable bullet is actually spiraling in
initially where a marginally stable bullet isn't.
I guess this may make sense if the precession rate of the bullet
is slow enough so that it is laterally displaced resulting in a spiral
path. The precession rate will be proportional to the drag divided by
the angular momentum along the spin axis, so if this angular momentum is
high (high spin) the precession rate could be low enough to cause this in
an "overstable" bullet where in a marginally stable bullet it would precess
too fast to notice the displacement.



# That's exactly what happens when a bullet is spun a bit too fast when
# it leaves the barrel. Its centrifugal force is just enough to cause it
# to wobble, but as soon as its spin rate slows down enough to where the
# centrifugal force no longer causes it to wobble, it will fly point on
# quite well. During the time the bullet wobbles a bit and its axis isn't
# tangent with its trajectory, it presents different attitudes to the
# atmosphere it's flying through, so it tends to take a spiraled path to
# through the air. When its RPMs are a bit lower, it now flies straight
# through the air in a much straighter path.

OK, I understood your theory of unbalanced bullets and overstabilization,
but I was thinking of the perfectly balanced bullet case.
Even a perfectly balanced bullet will wobble - precess and nutate
to a greater extent according to the drag to spin ratio.

Does Mann's book show a spiraling path to the target?
How big a spiral? Does the spiral increase and then converge, or
does it just diverge? What would the nature of the forces be that
would make it converge again if it does? If it diverges for a
while and quits, then it seems that the observed divergence would just be
worse at long ranges, unless the spiral is totally reproducible.

I was brushing up on the chapter on motion of a rotating projectile in
Moulton's book on Methods of Exterior Ballistics (1920s) where he
did the theory associated with experiments similar to your Mann's
with projectiles fired through cardboard screens. Moulton discusses
the firings of 3" projectiles at Aberdeen Proving Grounds.
He does not address any translational motion or spiraling in his
theory except for drift due to rifling twist, and only deals with
measurements of the angles and periods of nutation and precession
and how these damp out with time. Here is a summary:
He derives the gyroscopic motion of the projectile and defines a
quantity "S" that is inversely related to the rate of spin (or
stability). The value can approach 0 as the spin increases, and can
reach a value of 1 where it is at the verge of total instability.
(It is also proportional to the torque on the bullet by the wind drag.)
The bullet's spin axis will make a small angle "theta" to the
bullets path that will increase and decrease between 2 values, theta1
and theta2. This action is called nutation, and its period "P" is
calculated and varies with "S" and the initial conditions which
determine the initial angles. Good projectiles and guns give
small inital values of theta, so the result for the nutation period
is P= tw/(v*sqrt(1-S)) where tw is the twist length and v the
velocity. Then there is precession where the axis sweeps out a cone
shape around the bullet path line. The bullet is found to transition
between different modes of wobble, a fast precession where the axis
sweeps a about 360 degrees each nutation period, and a slow precession
where it only sweeps a fraction, typically 1/4 a circle each
nutation period. There are 3 modes of this slow precession which
vary by the way the precession speeds up or slows down on each
nutation bob ( the precession is not a constant speed).
Next - how are these oscillations damped? Even if the velocity and S
were constant and the bullet moved in a straight line, the oscillations
would be damped in the following manner: The fast precession mode would
have theta1 and theta2 both decrease and merge together resulting in
a more stable configuration with the bullet pointed where it is
going. The slow modes would have theta1 and theta2 merge but increase,
resulting in a less stable situation.
Now add in the effect of changing v, S, and the effect of a curved
trajectory on the damping and the result is that all modes have
theta1 and theta2 approach each other and decrease toward stability.
The rate of this damping is expressed as an equation, but I have
not figured out how to calculate the coefficients quantitatively
yet. It is shown that a bullet will follow the path of its curved
trajectory so that theta(1,2 merged) remains a constant or decreases
due to increasing S downrange.

Overstabilization is discussed only in terms of a bullet where S
is too low a value to allow the bullet to follow the curved trajectory
in this manner. If this is the case I would expect to see an effect
that would increase down range, but it seems we don't see this in
practice.



# Over the years, I've heard all kinds of comments, theories and the like
# regarding the angle a bullet has while going downrange. For example, if the
# bullet is properly stabilized by its spin rate and is fired at an upward angle
# of, say 15 MOA (like for a target about 500 yards away), does the long axis of
# the bullet:
#
# Remain at +15 minutes up angle for its entire flight?
#
# or
#
# Stay parallel to its trajectory path and point down as the trajectory goes
# down?
#
# and
#
# Do rifle bullets and larger artilllery/naval projectiles have the same
# characteristics in this regard?
#
# I'm curious to know what others believe.

I have been thinking of the same problem over the years, but I have no
really good answers. However, I have a couple of data points, both
derived from military experience.

1. I once saw a high-speed film of a projectile in flight, I think it
was 155mm, but it may have been bigger. The nose of the projectile was
running in a circle around the direction of flight, not very large,
but obviously following a corkscrew trajectory.

2. The 107mm mortar is not fin-stabilized as most mortars are, but
spin-stabilized. The initial angle of flight is about 45 degrees, yet
it comes down with the nose first.

A rifle bullet is governed by the same laws as a larger projectile,
but the relative magnitudes between the air forces, gyroscopic
effects, and gravity need not be the same. A projectile of large
diameter has a much larger moment of inertia, of course, and the
ballistic coefficient is larger, meaning that inertia has relatively
more influence than the air forces. Nevertheless, if the projectile
is properly stabilized, I believe rifle bullets and military
spin-stabilized projectiles will show approximately the same
behaviour.

The reason for this, I believe, is that if the spin is appropriate,
the balance between the gyroscopic forces and the air forces is such
that the projectile will either tumble, do the corkscrew motion with
its nose, or align itself with the direction of flight (which could be
viewed as an infinitesimally small corkscrew motion).

The corkscrew motion probably comes from the fact that if you push at
a gyroscope, it will respond with a movement in a direction at right
angles with your push. If the air forces (drag) tries to push the nose
further out of alignment with the trajectory, it will respond by
moving the nose at right angles to the push. Thus, it will start to
move in a circle. I have not done any calculations, but I would think
that after a while (if it is properly stabilized) those small
oscillations induced by either a change of direction of fight or any
crosswind, will die down, and the projectile will align itself with
the new direction of flight. As the rifle bullet is travelling in an
approximately parabolic trajectory, the direction of flight is
continually changing, so I would expect a very small corckscrew motion
at all times, but aligned with the instantaneous direction of flight.

Hopes this makes some sense. I really should go read Dr. Mann before
shooting my mouth off, I guess.



: What do you mean by 'spiraling'? If you're saying that it's doing the
: equivalent of a barrel roll done by aircraft, I can't see the physics
: allowing that motion of the bullet.

Neither could someone else about ninety-some years ago. So he made some
very interesting tests.

Read Dr. F.W. Mann's Book, `The Bullet's Flight from Powder to Target.' It
has excellent examples of this. Thin paper sheets placed every few feet
between muzzle and 100 yards show the exact spiral path of the bullet.
It even shows how the angle of the bullet relative to its down-range path
is determined. Great reading. Even though it was first printed in 1907.
Physics hasn't changed much since then.



# Hey Guys:
#
# I can see how aerodynamic effects and the forces created by
# the center of mass and center of aerodynamic pressure being
# in two different places on a bullet can cause the "flight path"
# to be affected.
#
# I'll even buy this spiral flight path thing HOWEVER the great
# question that was never answered (at least this time around) was:
#
# "But why would the spiral be **different** every time?"
#
# (remember, group size is a function of each bullet following a
# different flight path; not that the flight paths in general are screwy)
#
# In other words, if each bullet consistently follows the *same*
# "spiral path" around the arc of flight, you would expect to see
#
# - bullet holes at different relative positions for different distances
# - different group sizes (in moa) the further you go out due to
# differential environmental effects (wind, etc)
# - different flight paths due to each bullet being different
#
# but not *smaller* (in terms of moa) group sizes!!!
#
# Or are we claiming that the dispersion around the *spiral itself*
# gets smaller the further out you go????
#
# This wouldn't seem to make much sense . . .
#
# A spiral path in and of itself- even if the spiral gets smaller- may
# explain how a *single* bullet tends to "home in" on a given
# flight path
#
# BUT
#
# does not explain how *successive bullets* follow/don't follow
# each other more or less closely!
#
# Did I explain this right?
#


The difference in muzzle velocity between rounds causes the bullets to
go through the paper at close range at different points of the
spiril. You will see this more frequently as time goes by due to the
numbers of tight twist barrels being used in this fad of shooting overly
heavy, long bullets. Shoot a 55 grain bullet out of a 9 twist barrel
etc. There has been posts in this thread indicating that the dispersion
of shots would be in seconds and minutes of angle proportionate to the
distance checked. Then I ask why not check every thing at short range
and eliminate shooter error. We shot 18000 rounds of 50 cal ammo during
a contract. The guns were sighted in and function tested at 100 yards
and averaged 1.5 moa groups. When these same guns were tested at 600
yards you would expect the groups to run 1.5 moa or 9 inches. The 600
yard targets ran as small as 3 inches and never any larger than 6 inches
as an average. Any that shot larger than 9 inches were inspected and re
tested.

With your bs theory you'd have us believing that even old rounds like the 220 Swift, 257 Weatherby Mag,25-06, and host of others that can push light bullets to near or over 4000 fps (some with 10 twist which puts us damn close to the 300K rpm) were/are horribly inaccurate even at long distances.

I think not Gibby.

Now you have lots of reading to do and thinking. I'll bet you all that Gibby gives one of his bs replies. Some paraphrase or something.

Larry, I think I might have inadvertantly set the stage for misunderstandings in this thread. I said "relative fast velocity" when maybe what I SHOULD have said was something like "fast enough to shoot varmints".


Yup Gibby, even your own forum members are tiring of your constant rpm bs. You just can't see the lights.

First off Larry, that the little test Joe showed in the chart above DIRECTLY correlates to your comment about 8 twist being the desired rate for the bullet in question, and he showed you that it 'taint necesarily so. If you can't see that, you might as well forget trying to understand what I'm about to tell you. That test revealed some interesting results, can you explain why? You throw books that you probably haven't even fully understood at us and say WE are the ones who don't understand your theory. Let me show you, in ballistic terms with which you claim to be familiar, why your theory is innacurate in its ability to describe what is really going on with our cast bullets at HV, and you'll see that, outside of extreme cases, accurate, linear flight paths have nothing to do with the bullets being out of balance or not "overspinning" them.

When a spin-stabilized projectile pops out of the muzzle, it is accompanied by two different types of barrel harmonics and about 40% of the powder energy in the form of muzzle blast. These forces combine to make the bullet yaw slightly in a random direction upon exit. The aerodynamic forces on the nose of the yawing bullet are countered by the gyroscopic forces of the angular velocity, which react (as a neat function of gyroscopes) at 90 degrees to the wind force against the yawing nose and slightly ahead of the center of gravity of the bullet, provided it is spining fast enough, moving fast enough, and of the appropriate shape. This perpendicular force acting on the center of pressure of the bullet ahead of the center of gravity is called the Magnus force, and is the most important force for keeping the bullet stable. Static stability is balance, dynamic stability is the balance of the magnus force against yaw, a setup of opposing forces made possible by the gyroscopic force of the rotation. I will assume you've read and understand enough about this to know about the spiraling nose, the different attitudes a bullet can have in flight, and why, so I won't go into ALL of the forces affecting the bullet, only those necessary to stabilize one. So, there is a stability factor for each bullet at launch that must be met or the bullet will fly off in an ever-increasing spiral, usually in a BAD way, and not at particularly high velocities either. If the static AND dynamic balance is sufficient to reach a minimum stability factor, the yaw is cancelled out usually within about 5,000 caliber lengths from the muzzle, which is not very far. If the bullet is dynamically stable at muzzle exit, it will virtually be dynamically stable for the remainder of the useful range. As forward velocity decreases with range, the spin rate deteriorates proportionally much less, so the damping effect of the magnus force increases and the bullet flys even more true, leading many to observe "going to sleep" of bullets at longer ranges. This actaully begins to occur just a few yards from the muzzle if things are done correctly. If the statically balanced bullet is spun faster than the minimum for dynamic stability at muzzle exit, the only real negative effect is that the bullet will maintain the same orientation downrange as it did when leaving the muzzle, meaning as it goes "over the top" or passes the apogee of the trajectory it will be flying nose-up, which increases the yaw of the nose, rather than the nose turning to "follow the arc" as it does when not overspun. This is only a significant factor when shooting at extreme upward angles, as you would with long-range artillery, not with sporting rifles which under most conditions will be fired fairly close to horizontal. The conclusion is that the only things that will cause a bullet to "cone" as it goes downrange are loss of static balance or loss of dynamic balance. Static balance is lost when a bullet is damaged at launch, out of balance badly, or experiences more yaw forces coming out of the muzzle than the dynamic balancing "system" can handle. The other possibility is that the dynamic force or static force is interrupted by a phyical collision with something, the dynamic balance is overcome by a shift in the magnus force to the rear (overturning moment) due to aerodynamic forces that come into play as the bullet is "retarded" downrange, such as going subsonic.

So, in review, the bullet's dynamic stability reduces the yaw of the nose (spiraling of the nose around the flight path while the CG point follows the line) until the bullet has almost no perceptable wobble by 5,000 caliber lengths. Dynamic stability depends on forward motion, rotational motion (gyroscopic effect), and the magnus force to be in balance, and the rotational motion (angular velocity) need only meet a minimum for the "system", anything over the minimum isn't necessary but is a bonus for horizontal shooting. In fact, as the angular velocity increases, the the distance required for the launch yaw to be dampened DECREASES, meaning the bullet "goes to sleep" sooner, because it actually increases the magnus force by increasing the "lift" due to air moving across the rotating nose of the bullet. "Overspun" really only means that it is spinning faster than necessary, not that it is spinning so fast that a (insert negative effect of your choice or invention) begins to occur. In fact there aren't any negatives from the 'overspinning' unless your launch sucks and throws the bullet out with so much yaw that it cannot possibly become dynamically stable, such as launching froma damaged crown or at the worst possible point in a vibration curve. If the bullet isn't statically balanced, there is no hope for it either, and it will fly out in ever-increasing circles until somebody shouts "Eureka! There's an RPM threshold that affects all bullets fired over 144K RPM! It MUST be that pesky dynamic balance making wild sprirals out of our trajectories like so many unbalanced car tires! We must reduce our rifling twists to compensate for the fact that we have no idea what's really going on or how to fix it!". What REALLY is the issue is there is a STATIC balance problem due to poor loading techniques that is causing excessive yaw at launch, and dynamic balance never had a chance. DON'T blame dynamic balance issues for causing the problem due to "overspinning", it's the STATIC balance that's the bugaboo, and this is why the RPM Threshold Theory cannot be substantiated.

The "overspinning" only serves to increase the magnus force and better stabilize a statically stable bullet. "Overspinning" also serves to DAMPEN static balance imperfections rather than increase them as the RPM Threshold theory dictates, unless the static balance imperfections are so great or the yaw angle at muzzle exit is so great that they "cam over center" the dynamic balance force (the bullet nose yaws beyond the point where the dynamic stabilizing component can lasso it back on course), in which case the bullet sprials off in to RPM Theory land, causing some pretty wild, non-linear group dispersions downrange.

As you should be able to see by now,the RPM Threshold really isn't a balance issue exacerbated by too much rotational velocity, it's a point at which irrecoverable yaw is induced by a poor launch, and in fact there is not ENOUGH spin to induce sufficient magnus force to dampen the spiraling out of control. EVEN A PERFECTLY, STATICALLY BALANCED BULLET WILL "CONE" IF THE DYNAMIC BALANCE IS THROWN OFF AT SOME POINT IN THE TRAJECTORY, therefore coning is not necessarily the result of static balance issues as the RPM Theory dictates. If the magnus force shifts to "at" or "behind" the CG, or the bullet shape is wrong or changes during launch, the bullet will become dynamically unbalanced resulting in uncontrolled yaw. Uncontrolled yaw will deflect the bullet aerodynamically and in some cases make it trace the path of the surface of an expanding cone.

So above a certain forward velocity (exactly what point depends on the "system"), it gets more and more difficult to launch bullets without excessive yaw. Unbalanced bullets make the yaw even worse, causing non-linear dispersion. At this point someone will say "A-HAH! So you just substantiated the RPM Threshold theory!" but in fact this isn't the case, because the theory states that the non-linear dispersion is due to increased centrifugal effect from the unbalanced bullets being overspun. Actually any so-called "RPM Threshold" effect is observed ANY time a badly out-of-balance, damaged, or excessively yawed bullet exits the muzzle, although normally we call those "flyers" if they are anomalies, and "piss-poor shooting" if those "flyers" are the norm for the group. Overspinning only serves to correct imbalances (with possible exception of certain "nodes" in the RPM spectrum, of which I don't know any studies or information), but no amount of practically achieveable spinning will overcome a bad launch, a badly damaged bullet, or an unbalanced load, so the "RPM Threshold" becomes an excuse, to be blamed on "too much spin magnifying the unbalanced bullet".

I had the opportunity a couple of years ago to spin-balance some of my cast bullets and compare them directly to some common copper-jackeded bullets, and in fact in most cases my cast bullets were better. If static imbalance and centrifugal force were responsible for non-linear group dispersion, the jacketed bullets would certainly have shot worse at similar velocities, but they did NOT. The reason? My cast bullets were getting damaged and so were not coming out of the muzzle as true and balanced as the jacketed ones after all (even being better when loaded into the breech end). Now, when I identified and repaired the cause of the bullet damage affecting my cast projectiles, the group dispersion became linear, actually a little LESS than linear, tested at 50, 100, and 200 yards, albeit on different days.
Do poorly balanced bullets shoot better at low RPM/velocity? Yes, because they don't yaw as badly coming out of the muzzle and there is some chance for the (even reduced) gyroscopic stabilizing effect to take place and, combined with the magnus force acting ahead of the center of gravity to minimize the nose spiral, normalize the bullet to at least a reasonably tight, non-expanding helical path.

The yaw is what gets you as you increase velocity, not how fast the bullet spins as it goes downrange. So why is it easier to go faster with accruracy by simply going to a slower twist? Because the yaw gets you less. Why does the yaw "get" you less? I'm not really sure, but study of recovered bullets indicates that slower twists put less torsional stress damage on the bullet at muzzle exit. There are loading techniques that minimize this stress and allow less yaw at HV, fast-twist launch. Maybe, if even more really deep study is done here, we might be able to establish a Twist Rate Threshold Theory that will more accurately identify what's causing our HV accuracy issues.

So FINALLY, it's easier to shoot HV with slower twists with cast bullets, but it's all in the launch, not due to "overspinning". If you learn how to tame the factors affecting the yaw at launch, you don't have to worry how fast the bullet is spinning once it leaves the barrel as long as it is fast enough for dymanic stability to take place.

Those two separate barrel harmonic forces I mentioned in the beginning have LOTS to do with taming launch yaw, pressure curve shape has a lot to do with the rest. Like I said before, even on this thread I think, it's all about INTERNAL ballistics. If you start with good castings and get the launch right by controlling the mechanics and the internal ballistics, particularly what immediately proceeds from the first spark, the external part will take care of itself and you needn't get your knickers all knotted up about a particular rifling pitch.

Gear

Gear,

My head is rpm'ing ,errrr I mean spinning,from that one. Very good synopsis.

a couple of points.

a longer nose will give more area for the imbalances [yaw,wind,whatever] to work on.

i have read all of dr manns book.
i do not remember him showing any corkscrewing going on in any of his paper tests, i do remember him showing yawing and some types of keyholing in some circumstances.

quote:

Originally posted by Lamar:
a couple of points.

a longer nose will give more area for the imbalances [yaw,wind,whatever] to work on.

i have read all of dr manns book.
i do not remember him showing any corkscrewing going on in any of his paper tests, i do remember him showing yawing and some types of keyholing in some circumstances.

You talking about the test where he placed thins sheets of paper at spaced interviews and shot through them?

I like how he recovered bullets undamaged shot into oiled sawdust. I believe Gear is going to try that. I've love to see some bullets fired at HV, high pressure, from a fast twist recovered undamaged. I believe the could tell us a lot.

quote:

Originally posted by Lamar:
a couple of points.

a longer nose will give more area for the imbalances [yaw,wind,whatever] to work on.

i have read all of dr manns book.
i do not remember him showing any corkscrewing going on in any of his paper tests, i do remember him showing yawing and some types of keyholing in some circumstances.

+1 on the longer nose making things worse, and I think that's part of the reason that excessively long bore-riders get a little twitchy when pushed too hard (slumping unevenly happens too, as recovered bullets show, but that's exacerbated greatly by the long nose itself). Ogive shape which affects center of pressure location is the reason for the differences in stability. Needlenose bullets move the CP back toward the CG, making it easier for the magnus moment to turn the bullet away from the yaw rather than into it. If the magnus moment acts behind the CG, it adds to the yaw rather than subtracts from it, turning the bullet sideways and often destabilizing it so that it "cones". Fat, round nose bullets, from what I have read, tend to be more stable, although they can be more sensitive to deflection of course due to yaw, changing POI but not necessarily group dispersion. This is one thing I haven't tested personally, not having any super-pointy cast bullets to use.

I don't remember Dr. Mann finding anything exraordinary about helical spirialing either, but the yaw itself is indicative of that, and also indicative of how small it is. A statically and dynamically stable bullet can leave the muzzle with as much as a two degree nose wobble in addition to a significant "fixed" yaw and stabilize within a few yards. The nose wobble is not something you're going to see on paper. Part of my point in my explanation above was that the helical spiral traced by a stable bullet's nose early in the trajectory is very SMALL.

This animation will help explain what I'm talking about : http://www.nennstiel-ruprecht.de/bullfly/fig12.htm. Here's a good illustration of the path that can be traced by a bullet's nose close to the muzzle, note that it decreases, and note the distance traveled is in caliber lengths. http://www.nennstiel-ruprecht.de/bullfly/fig21.htm

Gear

quote:

Originally posted by SmokinJ:
You talking about the test where he placed thins sheets of paper at spaced interviews and shot through them?

I like how he recovered bullets undamaged shot into oiled sawdust. I believe Gear is going to try that. I've love to see some bullets fired at HV, high pressure, from a fast twist recovered undamaged. I believe the could tell us a lot.

It's on the project list, part of the "irritate my neighbor" campaign. They just LOVE it when I do HV cast shooting here at home. I really need to build a sound-attenuating shooting shack while I'm at it, and I wish I could do all that and have a 100, 200, and 300 yard range where the bench was a few yards from my gun room. Anybody wanna build a 300-yard warehouse with a 30', unobstructed fire lane down one side on my property???

Gear

yeah the paper testing.

i know the longer nose will show un lineal dispersion over distance.
i shot the rcbs 165 silhouette boolit in my 308 over increasing charges of imr 4895 starting at 28 grs and worked up noting group sizes.
this was part of an earlier lube test working with ceresin,bac,magma engineering lube,and a couple of others.

i could hold decent groups at 100 and 200 yds but once the groups exceeded 3" at 100 yds they were barely on an 8x11 sheet of paper at 200 and i couldn't hold them on a 4x4 piece of plywood at 300.

now once i upped the tin and antimony in the alloy i could shrink the groups again but as soon as i increased the velocity again the dispersion was once again askew at distance.

the addition of a higher bhn would only carry me so far and i could see no difference in my 4/6/90 aloy and lino-type at the higher charges.

the problem i had/have was/is capturing the boolits to try and determine whether i had nose slumping or if i was "overstabilizing"[corkscrewing] or just what was happening.
i stopped the testing after burning up well over 16 lbs of powder and testing about 8 different commercial lubes.
i never seen any leading from any of them btw, but the silhouette boolit is a pretty good fit to the rifle.

now.
if i had a 120-130 gr boolit made up [based on the rcbs silhouette boolit] just by shortening the nose, adding a bit more bearing length, and slowing down the powder burn rate,
i'm positive i could easily push the velocity envelope much further in this rifle.
and that's pretty much just by guessing at the design,based on shooting another boolit.
without measuring and stuff.

quote:

Originally posted by Lamar:
yeah the paper testing.

i know the longer nose will show un lineal dispersion over distance.
i shot the rcbs 165 silhouette boolit in my 308 over increasing charges of imr 4895 starting at 28 grs and worked up noting group sizes.
this was part of an earlier lube test working with ceresin,bac,magma engineering lube,and a couple of others.

i could hold decent groups at 100 and 200 yds but once the groups exceeded 3" at 100 yds they were barely on an 8x11 sheet of paper at 200 and i couldn't hold them on a 4x4 piece of plywood at 300.

now once i upped the tin and antimony in the alloy i could shrink the groups again but as soon as i increased the velocity again the dispersion was once again askew at distance.

the addition of a higher bhn would only carry me so far and i could see no difference in my 4/6/90 aloy and lino-type at the higher charges.

the problem i had/have was/is capturing the boolits to try and determine whether i had nose slumping or if i was "overstabilizing"[corkscrewing] or just what was happening.
i stopped the testing after burning up well over 16 lbs of powder and testing about 8 different commercial lubes.
i never seen any leading from any of them btw, but the silhouette boolit is a pretty good fit to the rifle.

now.
if i had a 120-130 gr boolit made up [based on the rcbs silhouette boolit] just by shortening the nose, adding a bit more bearing length, and slowing down the powder burn rate,
i'm positive i could easily push the velocity envelope much further in this rifle.
and that's pretty much just by guessing at the design,based on shooting another boolit.
without measuring and stuff.

Lamar,

That's what is going on with my 7 twist AR. Changing the alloy only helped a little and that shows me that it's not the rpm doing it because if it was it would do it with both alloys at HV. Anyways it wasn't until I did that blended powder test that I was able to move up the velocity ladder and with the softer alloy none the less. I love 4895 but feel it's poor powder to try to push things. Now buffer will let it push more.

Well I got your attention here I believe the question you asked about Mann is on page 185 and up. It goes for quite a few pages. He talks about the gyroscopic action, centrifugal force, and other things. Take a look at it again.

quote:

Originally posted by Geargnasher:

quote:

Originally posted by SmokinJ:
You talking about the test where he placed thins sheets of paper at spaced interviews and shot through them?

I like how he recovered bullets undamaged shot into oiled sawdust. I believe Gear is going to try that. I've love to see some bullets fired at HV, high pressure, from a fast twist recovered undamaged. I believe the could tell us a lot.

It's on the project list, part of the "irritate my neighbor" campaign. They just LOVE it when I do HV cast shooting here at home. I really need to build a sound-attenuating shooting shack while I'm at it, and I wish I could do all that and have a 100, 200, and 300 yard range where the bench was a few yards from my gun room. Anybody wanna build a 300-yard warehouse with a 30', unobstructed fire lane down one side on my property???

Gear

Rick Jamison said he use to cut both ends out of two steel 55 gallon drums and weld them together end to end. Then he would line them with regular insulation fiberglass and use a very coarse wire fence to hold the fiberglass in place. He made a leg frame work to set this apparatus on in front of his bench and believe he said the barrel was "just" in the mouth of it. He also said it deaden the noise quite effectively.

quote:

Originally posted by Geargnasher:

quote:

Originally posted by Lamar:
a couple of points.

a longer nose will give more area for the imbalances [yaw,wind,whatever] to work on.

i have read all of dr manns book.
i do not remember him showing any corkscrewing going on in any of his paper tests, i do remember him showing yawing and some types of keyholing in some circumstances.

+1 on the longer nose making things worse, and I think that's part of the reason that excessively long bore-riders get a little twitchy when pushed too hard (slumping unevenly happens too, as recovered bullets show, but that's exacerbated greatly by the long nose itself). Ogive shape which affects center of pressure location is the reason for the differences in stability. Needlenose bullets move the CP back toward the CG, making it easier for the magnus moment to turn the bullet away from the yaw rather than into it. If the magnus moment acts behind the CG, it adds to the yaw rather than subtracts from it, turning the bullet sideways and often destabilizing it so that it "cones". Fat, round nose bullets, from what I have read, tend to be more stable, although they can be more sensitive to deflection of course due to yaw, changing POI but not necessarily group dispersion. This is one thing I haven't tested personally, not having any super-pointy cast bullets to use.

I don't remember Dr. Mann finding anything exraordinary about helical spirialing either, but the yaw itself is indicative of that, and also indicative of how small it is. A statically and dynamically stable bullet can leave the muzzle with as much as a two degree nose wobble in addition to a significant "fixed" yaw and stabilize within a few yards. The nose wobble is not something you're going to see on paper. Part of my point in my explanation above was that the helical spiral traced by a stable bullet's nose early in the trajectory is very SMALL.

This animation will help explain what I'm talking about : http://www.nennstiel-ruprecht.de/bullfly/fig12.htm. Here's a good illustration of the path that can be traced by a bullet's nose close to the muzzle, note that it decreases, and note the distance traveled is in caliber lengths. http://www.nennstiel-ruprecht.de/bullfly/fig21.htm

Gear

I think you may have a point on the bore rider when pushed too hard. Think about slamming the rear of the bullet while it's in the bore with high gas pressure that compresses it. Remember we talked about that. So the compressed metal has to go somewhere. That somewhere with a bore rider would be the bore riding section and it may be forcing it into the grooves since a bore rider isn't suppose to be riding the grooves. If it does that unevenly we know what will result.

We need that perfect bullet trap.

Gear,

In that second link it appears the bullet actually gets better out at the further distance just like we talked about in another link I sent you.

quote:

So above a certain forward velocity (exactly what point depends on the "system"), it gets more and more difficult to launch bullets without excessive yaw. Unbalanced bullets make the yaw even worse, causing non-linear dispersion. At this point someone will say "A-HAH! So you just substantiated the RPM Threshold theory!" A-HAH! You did, in fact, just substantiate the RPM threshold.but in fact this isn't the case, because the theory states that the non-linear dispersion is due to increased centrifugal effect from the unbalanced bullets being overspun.Exactly what the rest of your dissertation states, you contradict yourself. However, you are correct; it is indeed an affirmation of the RPM threshold. Actually any so-called "RPM Threshold" effect is observed ANY time a badly out-of-balance, damaged, or excessively yawed bullet exits the muzzle, although normally we call those "flyers" if they are anomalies, and "piss-poor shooting" if those "flyers" are the norm for the group.No, the adverse effects of RPM are evident in all bullets, cast or jacketed at any velocity where the bullet is dynamically stable. It's why I referred joe and others to the simple explanation of such in Hornady's manual. There's even pictures so joe could understand but he can't. The RPM threshold is the point where the centrafugal force overcomes the dynamic stabillity (that is not saying it unstabilizes the bullet) and causes it to go off on a tangent or the spiral in a non linear fashion. Up to the RPM threshold of cast or jacketed bullets unbalanced bullets display varying degrees of inaccuracy.

It's why milsurp bullets aren't as accurate as commercial bullets because they aren't made as well(balanced) to begin with. At normal velocities both exhibit dynamic stability and linear dispersion. However, the imbalances of the milsurp bullet are more effected by the RPM and thus they are not as accurate. That is from the same barrel with the same identical load. The "launch" has nothing to do with it. It is the adverse effects of the centrifugal force of the RPM during the flight (that's external ballistics) that the inaccuracy occures. Overspinning only serves to correct imbalances (with possible exception of certain "nodes" in the RPM spectrum, of which I don't know any studies or information), but no amount of practically achieveable spinning will overcome a bad launch, a badly damaged bullet, or an unbalanced load, so the "RPM Threshold" becomes an excuse, to be blamed on "too much spin magnifying the unbalanced bullet".Overpsinning increases the problem and magnifies the extent of the problem. If you read in the ballistics books I mentioned you will find that out. Also practical experience will prove it also.

I had the opportunity a couple of years ago to spin-balance some of my cast bullets and compare them directly to some common copper-jackeded bullets, and in fact in most cases my cast bullets were better. If static imbalance and centrifugal force were responsible for non-linear group dispersion, the jacketed bullets would certainly have shot worse at similar velocities, but they did NOT. The reason? My cast bullets were getting damaged and so were not coming out of the muzzle as true and balanced as the jacketed ones after all (even being better when loaded into the breech end). Now, when I identified and repaired the cause of the bullet damage affecting my cast projectiles, the group dispersion became linear, actually a little LESS than linear, tested at 50, 100, and 200 yards, albeit on different days. I'll bet the "damage" was lessoned by reducing the velocity/RPM.

Do poorly balanced bullets shoot better at low RPM/velocity? Yes, because they don't yaw as badly coming out of the muzzle and there is some chance for the (even reduced) gyroscopic stabilizing effect to take place and, combined with the magnus force acting ahead of the center of gravity to minimize the nose spiral, normalize the bullet to at least a reasonably tight, non-expanding helical path. They shoot better at lower velocity because they do not get damaged as much in the barrel as you mention. Thus they are less imbalanced and there is also less centrifugal force because the RPM is less. Gear, you are doing everything you can here to perfectly describe the RPM threshold; above and below it. Also, as I'e told you I dn'tt know how many times, the RPM threshold effect occurs during the external ballistic phase, not the internal. Get out of the barrel and study external ballistics and you will see that.

The yaw is what gets you as you increase velocity, not how fast the bullet spins as it goes downrange. Duh!!!! isn't one because of the other? The spin is directly related to the velocity since the twist is constant. So why is it easier to go faster with accruracy by simply going to a slower twist? Because the yaw gets you less. Why does the yaw "get" you less? And the answer is; the faster bullet from a slower twist has less RPM than the same from a faster twist. Less RPM equals less centrifugal force to act on the imbalances. The slower twist also generally does not damage a cast bullet as much with a given load. This also results in less of an imbalance for the lessoned centrifugal force to act upon. I'm not really sure, but study of recovered bullets indicates that slower twists put less torsional stress damage on the bullet at muzzle exit. There are loading techniques that minimize this stress and allow less yaw at HV, fast-twist launch. Maybe, if even more really deep study is done here, we might be able to establish a Twist Rate Threshold Theory "Twist rate theory"???? Sure sounds like you are simply renaming the RPM threshold since RPM is directly related to twist. However, once again you are stuck inside the barrel and what happens there. The centrifugal force occurs in the external ballistics phase. Get out of the barrel and see what is happening gear.that will more accurately identify what's causing our HV accuracy issues.

So FINALLY, it's easier to shoot HV with slower twists with cast bullets, but it's all in the launch, not due to "overspinning". Not true. Even slower twist barrels will have an RPM threshold with cast bullets. With the slower twist the velocity can be increased before the threshold is reached is all. If you learn how to tame the factors affecting the yaw at launch, you don't have to worry how fast the bullet is spinning once it leaves the barrel as long as it is fast enough for dymanic stability to take place. Then why aren't we all shooting cast as fast and as accurately as jacketed? We aren't and there are sound scientific reasons why were are not (yet).

Those two separate barrel harmonic forces I mentioned in the beginning have LOTS to do with taming launch yaw, pressure curve shape has a lot to do with the rest. Like I said before, even on this thread I think, it's all about INTERNAL ballistics. Get out of the barrel into external ballistics. You know that or why the plagarized dissertation on "dynamic stability" which is a function of external ballistics? You really should make up your mind and quit disaggreeing with yourself. If you start with good castings and get the launch right by controlling the mechanics and the internal ballistics, particularly what immediately proceeds from the first spark, the external part will take care of itself and you needn't get your knickers all knotted up about a particular rifling pitch.Then why all this "discussion"? What happens in the barrel is very important and necessary to control. However, what causes aan imbalanced bullet to fly inaccurately occurs in the external ballistic phase, not the internal phase.

Gear

Larry Gibson

Gear

I see you’ve heartburn again because you made another stupid statement on the CBF and I called you on it. This is self evident because you run right back hear and post the crap you do here as you can’t post it there. Pretty immature……

Yes the test Joe posted revealed several interesting results. That test in no way disproved anything I said. It did agree with what I said about fast twists shooting light weight bullets well at close range. It also raised a lot of interesting questions about the conduct of the test itself (there was no explanation of sights used test conditions, test conducted at the same time or specifically the condition of the barrels). The 8” twist is the choice of thousands of National Match shooters with ARs. They also use 80 & 85 gr MKs; note the lack of that bullet there. Go back and read Joe’s argument about the different barrels I used (not that it makes a lot of difference when just measuring and comparing BCs and comparative accuracy [that’s comparing the accuracy of one load to another in the same rifle, not between rifles]).

However, the most obvious fact about that test was using the 90 gr bullet when it is only adequately stabilized in a 7” or faster twist. It was progressively less accurate in the 8 through 12” twist barrels which does not surprise anyone familiar with such (obviously the 3 of you are not). The author of the test obviously wasn’t aware either or he wouldn’t have included an “average accuracy” figure”. The exclusion of the most common bullets used in the 8” twist for accuracy also indicate a lack of knowledge regarding what is really used in ARs for accuracy. If the BC had been measured it would also have been progressively less. Had the test also been conducted at 20 yards I’m sure there would have been a large non linear dispersion also. Additionally had the test been conducted at 300+ yards the results would also have been different. The inaccuracy due to under stabilization was just as I said. The test itself was not stupid, however joe’s use of it was. He used another nonsensical analogy attempting to prove a point. His analogy did not come close.

You guys asked for the books/information on ballistics…….repeatedly. I gave you 3 examples from easy to understand to difficult. Now you complain about them because you can’t understand them? That too is pretty stupid. In joe’s case perhaps his father was right; he is a moron. Yes, I do understand all of them. The fact that you don’t and now complain about them is what you always do. The same as you didn’t like the answer I gave you last February to your question(look it up at CBF). You said I was wrong but yet if you knew the answer why didn’t you answer the question? The reason is you didn’t then know I was wrong and you don’t know now….because you don’t know the answer. The fact that you can’t understand any of the 3 books I gave, at your request answers the obvious question here……..

Your plagiarizing of the description of “Dynamic Stability” is commendable; however dynamic stabilization or the lack of is not the cause of the inaccuracy with regards to the RPM Threshold. The RPM threshold does not influence the dynamic stability of the bullet. I have always pointed this out in many posts saying the bullets are still stable and fly point on, they do not “tumble”. You come close to understanding with; “So, there is a stability factor for each bullet at launch that must be met or the bullet will fly off in an ever-increasing spiral, usually in a BAD way, and not at particularly high velocities either. “ . The problem with your plagiarizing dissertation on dynamic stability is you fail, either unknowingly or intentionally, to mention the adverse effect of the centrifugal force on imbalances in a dynamically stable bullet in flight. That is where the RPM threshold comes in. The “spiral effect”, which you and your 2 amigo’s have pooh-poohed for a couple years now, is from the centrifugal force acting on the imbalances of the bullet in flight. Note that even in the “spiral” the bullet flies point on which means it is still dynamically stable, just to a lesser degree caused by the centrifugal force of the RPM acting upon the bullets imbalances. You also are correct with; “not at particularly high velocities either”. As I have always said the RPM threshold can be lowered or raised.

Perhaps you are learning?

Larry Gibson

quote:

We shot 18000 rounds of 50 cal ammo during
a contract. The guns were sighted in and function tested at 100 yards
and averaged 1.5 moa groups. When these same guns were tested at 600
yards you would expect the groups to run 1.5 moa or 9 inches. The 600
yard targets ran as small as 3 inches and never any larger than 6 inches
as an average. Any that shot larger than 9 inches were inspected and re
tested.

Joe

Another stupid analogy (beginning to think your father was indeed correct). I don't know where you got that from. Some facts in there but based on the quote above I call BS

18000 rounds during a "contact" indicate M2 HMGs were used. Also with 4/1 ball/tracer. Now I've shot one hell of a lot of M2s in 40 years in the Army and 1.5 moa? Give us a break. Ain't going to happen even on single shot. Hell, Single shot, bolt action and Barret M82s won't do that with issue ball. Based on that I lend absolutely no credence to your entire analogy as it's all suspect as BS

Why don't you take a few years and study those book I mentioned without any of your stupd, moronic analogies. You might learn something.......I doubt it but you jut might.......

Larry Gibson