I've gotten into a nasty discussion with a shooting buddy that I need your guys' help with.
He insists he has a 6mm that shoots 3" groups at 100 yards(poor accuracy), but will shoot 1.5+/-" at 200 and 3"+/- at 300(better accuracy). He claims that particular gun needs some distance to stabilize the bullet. I asked him if the 100 yard bullet holes are keyholed or show some sign of an unstabilized bullet. He says no, nice and round.
Being an engineer, I tried to explain to him that a bullet, once fired and leaving its line of aim, will not remember where it was aimed and begin to head back for that point, get back on its aiming line and stay there. It is physically impossible and defies physics..

I need an expert here to tell me I'm right, please.

He says he had a round barrel fluted to make it stiffer, but thats another argument.

Your buddy knows not whereof he speaks. Maybe he shot a 200 group once that was smaller than his 100 yard group, but we've all done that at one time or another. Ask him to demonstrate it for you. Put up two overlapping targets, one at 100 and one at 200. Fire one group and see. (Talk him into making a big bet first. )

Ray

Ray

Alaska Jim: No your friend is wrong (thats what friends are for - isn't it?)! His Rifle cannot shoot 3 M.O.A. at 100 yards and then inexplicably shoot 1 M.O.A. at 300 yards!
If it consistently shoots 3" groups at 100 yards (in calm air and conditions!) it should consistently shoot 9" groups at 300 yards (in the same calm air)!
Tell him to let his barrel cool between all test shots, use windflags, a VERY steady rest, the same point of rest on his forearm for each shot, same grip, same trigger "SQUEEZE" and same EVERYTHING when doing his range work.
I have read a lot on this subject and it would take MANY pages to relay all of what I have read.
Further, on this same (similar?) subject I contend and often find myself discussing (arguing?) that a proper bullet, properly stabilized (correct twist rate [R.P.M.'s]) and flying at the proper speed will maintain its M.O.A. defined accuracy THROUGHOUT normal shooting distances. I define normal shooting distances as from 100 yards to 600 yards, and often further! These distances I defined are where the VAST majority of Rifle bullets are shot at targets. I know some people shoot further but these folks are the minute minority when all shot Rifle projectiles are considered.
In other words if your Rifle, or mine or your friends, shoots 3 inch groups (aprox. 3 M.O.A.) at 100 yards then it will shoot 9" groups (3 M.O.A.) at 300 yards - conditions being calm wind at all ranges!
I have proven this to myself on many, many occassions, along with my research on the subject is what I base my contentions on.
Some people make statements like "my Rifle shoots 2 M.O.A. out to 300 yards" leaving the implication or the question begging, then after 300 yards how does your Rifle know to change its accuracy???
The answer IS - IT doesn't!
The shooter and CONDITIONS change - NOT THE RIFLE or the bullet! Unless like I have previously described the bullet is being used (shot) at imroper velocity or not stabilized correctly - and these things are kinda hard to do anymore.
And be sure to GENTLY inform your friend he is wrong and relay the above shooting tips to him!
Friends are valuable - arguments though sometimes important are not valuable!
Stay warm over there!
Hold into the wind
VarmintGuy

I have to pencil in here and say that it is entirely possible for the gun to shoot out to 200 and 300 better than it will shoot at 100yards. Most of the time it has to do with the twist of the barrel and the ojive of the bullet he is shooting, or the jacket length of the bullet. When he says it is not stabilized at 100yards he is almost right. What he means in benchrest talk is that the bullet hasn't settled down yet. There are so many variables involved with the accuracy game that it is really hard to pin it down to a specific thing. There are 68grain bullets made on different length jackets that will all shoot different in the same gun. For example an .825 jacket on a 68 grain bullet won't shoot like a .790 jacket 68 grain bullet. A 7s ojive will shoot different than an 8s ojive bullet. A 14 twist barrel will shoot different than a 13 twist barrel, etc. That is why benchresters spend so much time at the range with so many different componets. You should ask the guy what bullet he is shooting and maybe he could try a different configuration to get around this problem. Call one of the custom bullet makers like Berger, or Barts, or Watson and discuss this with them. They will ALL confirm this and maybe steer you in the right direction.
Been there, done that. Got the T-shirt.

quote:

If it consistently shoots 3" groups at 100 yards (in calm air and conditions!) it should consistently shoot 9" groups at 300 yards (in the same calm air)!

Disagreeing with the above in a mild way, I'll go ahead and agree with Pegleg while I'm at it.

Reason for my lunacy is that in the case of VG's statement I'll say that in theory this is true, dispersion being theoretically linear. In reality the minor variations from shot to shot do not have linear effects at range, and dispersion will almost always be disproportionately greater as range increases. Velocity variations will have this effect as an example. BC variation from shot to shot is another.

As to Pegleg's ascertion, it is not unknown for groups to be somewhat inversely sized as a funtion of range up to a point, all else being equal. This is due primarily to the effects of fast cycle precession nulling beyond the 100 yard target. It is not a matter of dispersion so much as it is a function of an external force affecting dispersion being eliminated in the range of 150 yards or so. However, I think going from 3 MOA to 1 MOA is quite a stretch...in fact, I do not believe it.

Due to the precession experienced by a bullet it's travel takes the form of a helix, albeit a small diameter one. Depending on which expert you want to believe the deviation from bore centerline can have a magnitude of as much as 3/4" in what I'd characterise as an extreme example. That would translate to a 1.5" diameter helical path until the fast cycle precession nulls. What is left of this helix afterwards is smaller of course, and its magnitude is a function of Sg value, and it does not null...ever. The value above is extreme, and not representative of what normally occurs...think a radius of very small fractions of an inch about the bore CL. A complete cycle of this nature takes place in 25 to 50 yards, again it depends on which expert is quoting what facts...it varies....and is somewhat more pronounced in long for caliber bullets IIRC.

Getting beyond that, I have reservations that the reported accuracy is as stated, at least in magnitude. I also think that the average sporting rifle will not manifest the event in sufficient magnitude that allows the shooter to say without question that this is occurring. Statistical background clutter is likely more pronounced.

Anybody interested it studying the phsics involved may dig up a copy of "Modern Exterior Ballistics" by Robert McCoy. There is also "Rifle Accuracy Facts" by Harold Vaughn...I don't recall that Vaughn addresses this directly but his 6DOF depictions at various degrees of Sg allude directly to the phenomonon, and he does discuss the nulling of fast cycle precession. ANY precession causes deflection in the bullet's flight, and increases drag, hence lowering BC and Sg. As many as 4 precession modes may exist(to the best of my knowledge) in a bullet at any given time, fast cycle precession is caused by bullet imbalance and is the only one I'm aware of that will null. It's a squirrely world on the other end of the muzzle.

You may fire at will, I have nothing more to add to the discussion.

I agree with some of the comments offered, but maybe it could be the shooters mental attitude to shooting at shorter ranges.
The shooter subconciously thinks when shooting at 100 yds this aint so hard but at farther distances concentrates and shoots better due to the challenge of hitting a smaller defined target.

quote:

Anybody interested it studying the phsics involved may dig up a copy of "Modern Exterior Ballistics" by Robert McCoy. There is also "Rifle Accuracy Facts" by Harold Vaughn...I don't recall that Vaughn addresses this directly...

Actually he does address this in his book "Rifle Accuracy Facts";
p221 "External Ballistics Myths...5)...The only way I can see this happening is for the bullet to be launched with a large disturbance at the muzzle. While this can happen with magnum rifles with excessive muzzle blast pressure, it is very unlikely in the case of a 6BR or a 6PPC bench gun. Most likely, this is a case of poor statistics or a change in conditions."

I've seen some smart folk weighing in on both sides of this discussion. Some such as Bill Davis Jr while doubtful was already formulating a testing procedure while we were talking to verify his theory...smart guy. He also shared the fact that that corkscrew effect folks referred to is called "swerve" and was typically only a fraction of a caliber. Gale McMillan has written of this being common in his testing of their 50 cal rifles. Too bad he's gone and we can't go back and examine records more closely. If one is fortunate enough to have access to Franklin Mann's classic book "The Bullets Flight", one care read all about his experiments on the spiral paths that some bullets take.

I have a couple of things to add;
1) When folks are citing their observations, it's always with separate groups. ie. One group fired at 100 and another fired at 200 or 300. They're not tracking the same bullet. Statistics says it's entirely possible for a rifle to shoot 1 minute for one group then 2 or 3 minutes for the next. In order to confirm or refute the theory, I think it's important to be tracking the same bullets at both 100 and again at 200. It's now easily done (but expensive) with acoustic targets. This is the line of thought Bill Davis was on while thinking up his testing procedure.

2) One possible explaination would be a scope with parallax set for the longer distance, creating more error at the shorter distance.

my 30x378 shoots smaller groups @ 200 than it does at 100 nobody believes me until i show them.

I shoot much more accurately at longer ranges, but the reasons are psycho/physiological in nature. The farther the target is, the harder I "try" and the more I "focus", both mentally and physically.

My rifle and its round have absolutely nothing to do with the difference between short and long-range accuracy.

Poulsbo, my 338/378 agrees with you. However it does shoot pretty dang good at 100 most times.

There was an article in ST a couple of years ago where they reviewed the 30/378 Weatherby TRR and it shot noticeably tighter groups at 200 and 300 than at 100. As mentioned above I think it's more prevalent with bigger guns, like the various magnums and 50 BMG.

I will suppress my STRONG urge to laugh and make fun of you folks that think a bullet can somehow "think its way" into shooting better at 300 yards (when expressed in MOA) than at 100 yards!
I have shot literally hundreds of Rifles at varying distances and have never seen a Rifle perform thusly! Not ONCE - NEVER!
I mean how does the bullet know its past 100 yards and its time to change its flight path and get back to where the shooter really wants it to go???
I couldn't help it I just now burst out in a full howling laugh!
Someone please, Please PLEASE explain to me how these bullets make this decision to "get back on the right path"!
Once a bullet has dispersed there is no known force that will tell consecutive bullets "go ahead and disperse but don't forget to get back on course at 127.6 yards" or what ever distance!!!
Geesh do you people hear yourselves???
Gyroscopic effects do not explain this "alleged" phenomenon! If a Rifle is shooting a properly stabilized bullet into 3 MOA groups at 100 yards then magically at 300 yards the bullets ALL make the same decision in midflight to "quit dispersing" and all make the correct decision to change what ever course (line of flight) they are on at the time and somehow make this "change" and then go to a specific 1 MOA place at 300 yards - well... it just ain't happening gentlemen!
Again I burst into laughter at your naivete!
In order to disburse into a 3 MOA grouping at 100 yards (which is poor accuracy in anyones book to begin with!) then miraculously somewhere around 105 yards the bullets all "jump back into line" is stretching physics way beyond the breaking point!
It just ain't gonna happen!
Or perhaps one of you can relay just exactly at what yardages and WHY these bullets do jump back into line???
Do not forget that ballistics in fact is a very EXACT science!
As I write this and again suppressing a roaring laugh, I look up at my bookshelf and observe such thoughtful and well researched treatises as "The Bullets Flight From Powder To Target" by F.W. Mann, "Hatchers Notebook" by Julia S. Hatcher, "The Rifle In America" by Phillip B. Sharpe and legions of other books by Whelen, Page, O'Connor, Page, Sell, Ormond, Howe and many others! My memory would certainly have clarity regarding any Rifle that any of these experts came across that some how shot 3 inch groups at 100 yards and then miraculously became a tack driver at 300 yards!
Again - it ain't happening gentlemen!
And indeed in one of my tomes I do specifically recall the author going through the trouble of carefully aligning very thin paper targets with a surveyor scope. He then shot numerous rifles through this type alignment and your "miracle" bullets did not present themsleves! The gyroscopic phenomenon was observed as was expected but ALL BULLLETS from a particular Rifle "gyroscoped" the same! In other words at 100 yards the bullets were all "gyroscopically" at the same point in their rotation around the line of flight! Not some to the left and some to the right and some above and some below the line of flight! All bullets gyroscoped the same!
This rarely repeated "magic bullet" rumor will perhaps be layed to rest most emphatically by any doubters simply by them going to the link I am posting and reading the wonderful article on accuracy that was published some years ago in Precision Shooting Magazine. The interviewed benchrester is another EXPERIENCED Rifleman that lays to rest the contention that some bullets "go to sleep" at some rumored distance and some how miraculously "pick up" or "earn" or somehow "become" more accurate the further they fly!
Sheesh!
Heres the link: http://www.angelfire.com/ma3/max357/houston.html

Hold into the wind
VarmintGuy

I'm not rich by any means but I'll take all my money out of the bank and we'll make a little bet. First, we'll set up a target at 300 yards. Put any rifle of your choice on a benchrest setup with the crosshairs centered on the target. Then, without touching anything, we'll set up another target at 100 yards positioned so the crosshairs are centered on it. Now I'll let you shoot a group. All bullets will have to pass through both targets. Shoot as many shots as you like (more than one). Every time the 300 yard group is smaller I will give you $10. Everytime the 300 yard group is bigger, you give me $10. Keep shooting until one of us is broke. Any takers???

Ray

Hmmmmm. No takers? OK, here's the deal. I'll sweeten the pot. We'll put the first target at 50 yards!

Ray

Ray I will back you if you need any help. Lets double it to $20.
Butch

Hold on! You fellers are apparently not familiar with the little known "Pigeon" bullet made by the same guy who invented the Herter's wasp waist sonic bullet back in the 50's. He made a bullet that would self-correct it's course if it's was influenced by Newton's laws of physics. He passed away before it became popular. His epitaph reads, "Here lies Homer Pigeon, neither rain, nor sleet, nor running targets can keep me off course!"

Joe



Ray

Hey Alaska Jim.
You dont need an expert to tell you what you can find out for ya self, just get the rifle and shoot it yourself.
If it shoots ok for you then your mate is full of it. But if it shoots the same for you with big groups at 100 yds and better groups at 300 yds then you and your mate both can come with me and do some spotlighting.
Those bastard foxes and cats just stay outside of the beam of the spotlight at about 300 yds. They crouch down and use the shadow cast from bushes and stuff that the spotlight creates to crawl along and get away. So I will do the 100 yard hard shots and you blokes can do the easy shots out to 300 yards.

Seriously its not really worth the friendship to get into any nasty discussions, but, hey thats life, what we dont understand we wrestle with untill we do understand. So have a try of his rifle and proove it for yourself.

C.V.E.

I might believe what is hapenning on his targets, but I do not believe it is an exterior ballistic phenomenon.

Your friend could be fooling himself by shooting more carefully at 300 yards than at 100.

Or...

The target he's shooting at could be easier to aim at at 300 yards than at 100.

H. C.

what about yaw?

One obvious and well known influence to this phenomenon could be sighting equipment and shooter error. If the scope is parallax corrected for 300 yds and the shooter does not return his eye to "battery" after each shot. If his eye is positioned off centerline each time and does not make a correction, it could cause his groups to disperse at 100 yds due to optical error, but be correct at longer distances of 300. Just a WAG(Wild A$$ed Guess).I believe most of us are in agreement, Newton was correct.

quote:

Originally posted by AlaskaJim:
He says he had a round barrel fluted to make it stiffer, but thats another argument.

Actually that is correct. If done correctly, fluting a round barrel can make it stiffer.
It has the added benefits of increased surface area for cooling and a lighter barrel.
But that’s another argument.

I am going to give your friend the benefit of the doubt with his testing; solid rest, etc.
IF he is doing everything else correctly, parallax is a good guess.

Kudos Joe Young!

Usually parallax causes the opposite effect, (problems at longer distances) but if AO is set for 300yds and he doesn’t line his eye up EXACTLY the same every time it can and will cause problems just like this at shorter distances. But usually the target will not be in focus.

quote:

quote:
Originally posted by AlaskaJim:
He says he had a round barrel fluted to make it stiffer, but thats another argument.

Actually that is correct. If done correctly, fluting a round barrel can make it stiffer.
It has the added benefits of increased surface area for cooling and a lighter barrel.
But that’s another argument.

If you cut metal away from a barrel, it is more flexible than when you started. There should be no argument about that. The moment of inertia of an un-fluted barrel of diameter D is greater than the moment of inertia of a barrel of the same diameter D with the flutes cut away. Sheesh!!

quote:

Originally posted by JohnD:

quote:

quote:
Originally posted by AlaskaJim:
He says he had a round barrel fluted to make it stiffer, but thats another argument.

Actually that is correct. If done correctly, fluting a round barrel can make it stiffer.
It has the added benefits of increased surface area for cooling and a lighter barrel.
But that’s another argument.

If you cut metal away from a barrel, it is more flexible than when you started. There should be no argument about that. The moment of inertia of an un-fluted barrel of diameter D is greater than the moment of inertia of a barrel of the same diameter D with the flutes cut away. Sheesh!!

You are right, all other things being equal. You could have done without the sheesh.
Sorry I'm such a FI.

But, and it’s a big but, if he bought a heavier than standard barrel originally (#7 or 8) intending to flute it, it will be stiffer than the same length barrel in a smaller taper (#5 or 6) and probably weigh about the same.

Only way this could happen IMO is IF the bullets were luckily steered into a smaller group at the longer range by some "lucky" wind drifting! Might work for one lucky group, but not every group.

Just to throw more fat on the fire, if the groups are more vertical dispersed than horizontal, there is a (slim) chance that the old SMLE effect of "positive compensation" is happening. That is, the vertical vibrations of the barrel are tuned to just the right frequency to launch slower bullets slightly higher than faster bullets. Some wizard British armourer found a way to shim the skinny barrels of SMLEs way back when, to do this with the 303 cartridge, and the result was that the 1000 yd groups were better(by MOA measure, not absolute size) than the 200 yd groups. There is a method of finding these nodes with any target rifle, by shooting a series of shells having powder charges going upward by .2 gr increments, and noting which ones clump together vertically on the target. The middle charge of this group of three or four shots is theoretically your optimum charge weight for that particular range and load. PS:I still think the guy has a parallax problem in his scope, tho.

ok flippy#7 or #5 aluminum or stainless a fluted barrel is only stiffer than a barrel of the same weight for its leingth not of the same od at that length so if they weigh the same the fluted is stiffer but not by much and the posibility of any one flute being different or slightly out of place will make the bbl do realy odd things when it heats up. so just go bull for stiffness flutes are for marching bands

Crusher you confused me.
Butch

quote:

Originally posted by CRUSHER:
ok flippy#7 or #5 aluminum or stainless a fluted barrel is only stiffer than a barrel of the same weight for its leingth not of the same od at that length so if they weigh the same the fluted is stiffer but not by much and the posibility of any one flute being different or slightly out of place will make the bbl do realy odd things when it heats up. so just go bull for stiffness flutes are for marching bands

Maybe you should read my reply again.

quote:

Originally posted by Flippy:
But, and it’s a big but, if he bought a heavier than standard barrel originally (#7 or 8) intending to flute it, it will be stiffer than the same length barrel in a smaller taper (#5 or 6) and probably weigh about the same.

Crusher, what part of that don’t you understand?

quote:

From Lilja Precision’s website:
Fluted Barrels

Fluting barrels for both competitive target and hunting rifles is quite popular. There are two advantages to using a fluted barrel. Improved accuracy is one advantage because of increased barrel stiffness. If we compare a fluted barrel to one that is not fluted, both weighing the same, the fluted barrel is stiffer. This is because the fluted barrel will be of a larger diameter than the unfluted barrel of the same weight and length. Increasing the diameter of a barrel greatly increases its rigidity. Fluting may also allow for a longer barrel, if weight is a consideration. Another advantage to fluting is the increased cooling rate of the barrel because of the greater amount of surface area exposed to the air.

Flutes are also for Jethro Tull. And Ian Anderson plays in NO marching band…

I think that the confusing is coming from someone saying a fluted barrel is stiffer, which it's not. If you take two identical barrels and flute one of them, the one that is NOT FLUTED will be stiffer.

quote:

Originally posted by Neverflinch:
I think that the confusing is coming from someone saying a fluted barrel is stiffer, which it's not. If you take two identical barrels and flute one of them, the one that is NOT FLUTED will be stiffer.

That was me, the FI.

You also are correct, however you are about a week late...

quote:

Originally posted by JohnD:

quote:

quote:
Originally posted by AlaskaJim:
He says he had a round barrel fluted to make it stiffer, but thats another argument.

Actually that is correct. If done correctly, fluting a round barrel can make it stiffer.
It has the added benefits of increased surface area for cooling and a lighter barrel.
But that’s another argument.

If you cut metal away from a barrel, it is more flexible than when you started. There should be no argument about that. The moment of inertia of an un-fluted barrel of diameter D is greater than the moment of inertia of a barrel of the same diameter D with the flutes cut away. Sheesh!!

If people would read the posts, there would be NO confusion.

Except in my case...