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quote:

Originally posted by ALF:
Lapua have made a bullet, called the FOREX ... all things equal this configuration should have better penetration than a FN bullet? or am I wrong?

But it is not a solid, it is a soft nose that expands, right?

No comparison to the FN solid should be made.

The FN solid will be a much better penetrator than the Forex soft, obviously.

A lead-filled nose could not be as "nondeforming" as a copper monometal FN solid.

If the FN solid could be given a hollow base??? ... No good, as there goes the all-important mass and momentum.

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O.K. Now that you clarified that, how will you deal with the deformation of the hollow tail section which is bound to happen with tail slap of a round-nose-hollow-base bullet?

Drag reduction of the nose by a round instead of flat nose will lose the shoulder stabilizing, supercavitating stability that I know you don't believe in.

Hollow base, lighter bullet for length, fishtailing from deformed tail: no good.

I guess the concentricity issues of forming the hollow tail would be minor.

Upset obturation of the tail of the bullet to seal the bore should be good.

I SWAG a Flat Nose hollow-tailed bullet would be a better penetrator than any round nose hollow-tailed bullet.

I would be curious to read details of how that hollow base holds up upon firing also.

Hollow bases in my rudimentary experiments with solids appeared to have the same effect as Minie Ball projectiles and generated much more subjective pressure (sticky bolt lift, primer, and case head extrusion). I would assume this is a result of increased obturation drag due to flaring of the hollow "skirt". Perhaps proper design and material is the answer?

My thinking, with a solid, is why not deepen the grooves between the rear driving bands enough to shift the CG foward?

My ingenious brainstorm happended when trying to find the CG of a .375/300 BBS. Trying to balance the bullet on a knife edge shows that it is only slightly butt heavy. The CG is right at a shoulder of the crimp groove so I could not get the bullet to rest exactly.

This got me thinking why not draw up the best geometric shape, then move CG foward using groove depth?

If a rifle bullet was too nose heavy, wouldn't this cause severe "instability" as soon as it left the muzzle?
i.e. wouldn't gas push the bullets base to the side, way off line of flight

The only reason I can see for it is to allow for a "looser" fit between the driving bands/bullet shank to the bore as the hollow base will expand upon firing and provide the bore seal required. Shifting the mass to the front of the bullet will only reduce it's resistance to yawing ie the bullet will be more likely to tumble. Definitely NOT a match grade bullet design!

Mr. Scott,

I edited my post to add the last two lines while you were posting.

I was thinking that nose heavy may be best in dense medium, but since we are propelling the thing from the rear by expanding gas in a tube, when the base exits the muzzle escaping gas would push the base sideways in some direction?

If so, then we would have extreme angle of attack at close range.

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Alf,
I am sure Gerard has figured it out, and decided a slight boat tail base was all the center-of-gravity-help needed.

As said above, the expanding hollow base obturation could lead to pressure increase.
And the centering of the hole in the base adds another concentricity problem.

Surely the supercavitation of a flat nose is better than that of a round nose, and you have not picked up the shoulder stabilization gauntlet thrown down before you.

I am all ears if sumbuddy who know can explain why solid bullets for elephant hunting are not designed in the image of badminton birdies or Foster shotgun slugs.

John in SC,

My point exactly. This design is nothing more than a "modern" Minie ball, for mono-solids. It is aerodynamically a piss poor design!! Not sure if Alf has figured that our, from his initial comments he seems to have completely reversed (180 degree wrong) concept of aerodynamics.

It has been my understanding that spin stabalized projectiles fly better if the center of gravity is in the rear. Is my understanding wrong?

jwp475,

Your understanding is 100% correct. One wants to maximize the distance between the center of pressure (front of the bullet for all intrinsic purposes) and the bullets center of mass for most stable flight! This is basic aerodynamics, hence my comments on Alf's original posting.

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Alf,

quote:

The assumption is then that this bullet configuration is not sold as a long range bullet but sufficient for hunting ranges as are FN bullets.

Which is precisely what I was saying.

I do not see a round nose solid as the best pentrator no matter where the center od gravity is located. I attended the Linebaugh Seminar in Jackson,Miss the weekend of the 5-11 thru 5-13, and in wet newspaper the 500 Linebaugh,500 JRH,and the 475 Linebaugh shooting Hard Cast Flat point bullets out penetrated a 410 grain round nose solid fired from a 416 Rigby. The Rigby penetrated 46" the 500 JRH with a 425 grain Flat Point hard cast at 1384 fps and the 500 Linebaugh with a 525 grain hard Cast at 1091 fps went 50" and the 475 with a 420 grain flat point hard cast at 1382 fps went 49" and these are handguns
A flat point is the only way to fly IMHO. The round nose no matter where the CG is placed is more likely to wobble off line because of the nose shape IMHO........

jwp475,

I hate to break this to you, but flesh and bone ain't wet newspaper! Wet newspaper doesn't behave ANYTHING like flesh and bone, BTW. ACCURATE solid penetator penetration simulations are older than the last century and well documented! I suggest your course of study follow that path other than RIGGED marketing schemes!

Have a nice day.

I have killed enough large game with a handgun to have a good idea of thier capabilities,but that was not the crux of my post. The 416 Rigby with a trophy bonded solid and it's small flat point out pentrated every thing,but again that was not my point. The point was that the reason the round nose did not penetrate better was because it did not track straight and therefor the lack of penetration.

I forgot that PWS has experimented with moving the CG

https://forums.accuratereloading.com/eve/forums/a/tpc/f/...=802103885#802103885

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what i think is interesting is with the open base there is more powder room and maybe a better b.c. with the longer bullet???

when a bullet mushrooms the bullets center of mass moves forward regardless of design, no?

i like the premise of the bullet.

I played with hollow base bullets seven or eight years ago. I revisited the concept late last year when working with an ultra high BC 50bmg bullet for a tight twist barrel. The internal ballistics and external ballistics can be improved under certain conditions but terminal ballistics is another matter. Lowering the polar moment of inertia of the base of the bullet during penetration is not a good idea, imho.

The resistance to penetration of the bullet in soft solids is lowest with a cylinder shape. In realistic examples of bullets penetrating tissue, resistance to penetration is governed by the surface area exposed to the direction of motion and, to a lesser extent, by the speed in the medium. Higher speeds favour cylinder shapes and lower speeds favour angled shapes but cylinder shapes remain higher on the scale. We have discussed nose shapes to distraction, this is old hat.

I remember a lot off writing about this bullet when it came out, what, 10 years ago? What I remember from back then, was that the shape of the bullet was made to be more stable through branches and brushes between the muzzle and target. I tested it in phone-books, but was not impressed either by penetration, weight retention or the fact that it did tumble inside the books. It never was a hit, and has not been imported to Norway for some time - I actually belived it was discontinued.

Would it work better in a solid? I do not know, but the bullet gets very long for caliber, and - if it was a good idea, I would think it would have been a hit a long time ago....?

Hallo Alf,

You asked about the Lapua Forex. Therefore I send You some Pictures.

Bent Fossdal wrote “What I remember from back then, was that the shape of the bullet was made to be more stable through branches and brushes between the muzzle and target.†And I just remember the same.

The Lapua Forex was overly complicated and expensive to make, so it never really appeared in Volume.

To Your question about Stabilisation, I just can say Spin stabilisation works in Air, but not in Meat, as Meat is about 800 times denser, but once it enters the Meat the Bullet spins not 800 Times faster! That Air is compressible but Meat is not, aggravates the Situation. A well constructed Bullet utilises Shoulder stabilization. Round nose fail:



From the Elefant head shot thread I actually thought about a Dart stabilized Bullet, but that one would not spin. I have some heave alloys at Hand (double then Copper, denser than Lead) that could be used, but they also would eat the Barrels Lands. Therefore a Smooth bore would be fine, with an “Accelerator Designâ€, i.e. saboted, one could build very short an powerful Rifles, to suit the Needs of all Ulriks in the World.

Lutz M

I would think that to "form stabilize" a projectile within the media of flesh and bone would require the CG to be much more significantly forward of the CF than just slightly.

Anyone who knows better can correct me but it seems intuitively obvious that the stability achieved by a CG slightly forward of the CF would easily be disrupted by a small overturning moment on the bullet nose. Also, a form stable bullet would have to be self correcting to achieve straightline penetration and each correcting event may appear as path deviation.

The idea of a form stabilized bullet is sound, the practice may not be practial. It wasn't in my rude tests.

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quote:

Exactly why during the narrow channel phase of penetration a RN actually has a smaller temporary cavity than a FN and only once the RN becomes unstable does the Temporary cavity diameter go up and energy dump exceed that of the FN.

Alf,

RN miss a Shoulder and therefore no Shoulder stabilization can occur, hence they tumble.

Before they tumble according to the lower Drag, compared to a Flat Nose, they push less Meat aside, than a FN.

After they tumble from the unstable Equilibrium they turn about 90° toward a stable Equilibrium and further penetrate sideways. So positioned their Cross section greatly increases an they push much more Meat aside and penetrate much less, compared to a shoulder stabilized FN, that penetrates straight.

Interaction and Cross section are linear related, Penetration relates 1/Crossection or linear with Sectional Density.

Nothing comes less pay. You can max either Interaction or Penetration, not both together!

Lutz M

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Gentlemen,

This sounds like an interesting project for us to do, as we have the lathe, and can pretty much design it anyway we wish.

This might be after the summer though.

Any suggestions as to the design we should do would be appreciate it.

- Round nose or flat point - or both.

- How long should the cavity be - our bullets will be all made of either copper or brass - we could do both, and see if there is any differences.

- Does the caliber matter? If so what caliber should we try.

How manny should we try shooting?

Your thoughts would be appreciate it.

quote:

Originally posted by Saeed:
Gentlemen,

This sounds like an interesting project for us to do, as we have the lathe, and can pretty much design it anyway we wish.


This might be after the summer though.

Any suggestions as to the design we should do would be appreciate it.

- Round nose or flat point - or both.

Both of course so Alf will see the flat is better than the round nose, once and for all.

- How long should the cavity be - our bullets will be all made of either copper or brass - we could do both, and see if there is any differences.
What penetration medium? Texas heart shots on dead buffalo? Whatever the medium, please do both brass and copper. Cavity should be at least twice as long as the Forex, relative to total bullet length, but maybe with a slightly thicker "skirt" around the cavity. No lead in your bullet nose, after all.


- Does the caliber matter? If so what caliber should we try.

.375 caliber of course, loaded at standard .375 H&H velocity equivalence, or faster.

How manny should we try shooting?

at least 3 or as many as 10 each in brass, copper, RN, and FN, all at same weight and velocity. Sample size will depend on your time and patience, but the more the better of course.

Your thoughts would be appreciate it.

What penetration medium?

quote:

Originally posted by ALF:
LUTZ:

Now if you take a RN bullet and you make it mass forward that too would dampen out angle of attack effect, it's like a javelin or unfletched arrow with a heavy tip

Alf,

any solid (non deforming) Non ball bullet (Sphere), i. e. lengthy one, that is neither designed with Shoulder stabilisation (FN) or Dart stabilisation (Flechette with rear Fins) will at the slightest Tilt angle or smallest uneven Target see a destabilizing Torque, resulting from a Distance between Gravity center and the Stagnation Pressure on the Bow.

Remember only the wetted Front contacts the Meat, Blood Water or whatever soft Solid or Fluid You shoot it in. So the Torque would turn the Bullet until it reaches a stable Equilibrium between Forces.

All these hollow Tails will not at all meaningful effect Stability, as the Bullet travels in a Water vapor cavity.

Saaed,

If You like to put Your Lathe to Work You might want to try a Dart stable Design out of a Cylinder with a hollow Tail for Your Shot gun (must have removable Chokes removed to present a straight Bore, otherwise You ruin the Shot gun). That will without any spin be stable

Lutz M

3 copper FN and 3 copper RN darts, 6 dead buffalo to Texas-Heart-Shoot.

The FN darts will pass out the throats reliably.

The Round Nose darts will be stopped in the guts.

Shooting 10 of each type is no problems.

We need suggestions of what we should use for penetration medium.

Please bare in mind we are in an door, underground tunnel - so water is not an option, as some nincompoop standfing behind me just suggested!

We need something that can is easily obtainable, and can be re-used.

Blocks of paraffin/wax, petroleum derived, melt them down and reuse from your own molds, stack them in a row, put a piece of thin masonite or cardboard or paper between them as a witness to keyholing.
The "Bullet Test Tube" is just wax.

Ordnance gelatin would be best, of course.
Or dead buffalo and elephant.
Nobody wants to hear about my "iron buffalo" of waterbags and plywood boards alternating, but that would quickly tell if the RN or FN darts would track true.

In the iron buffalo

I just made a few phone calls looking for paraffin wax.

Minimum order quantity is a 20 foot container!!??

I am sure I will be able to find a re-seller. Apparently they sell them in bags of 50 Kgs.

Anyone has any idea of how much of this we might need?

http://www.thebullettesttube.com

They claim that 4 or 5 feet of this wax will stop a .375 H&H solid: probably a round nose would exit the side of the tube.

They claim that it only takes about 3/4 the depth of their wax versus ordnance gelatin to stop a bullet (soft point expander). I.e., multiply the depth of penetration in The Bullet Test Tube by 1.34 to give the estimate of depth of penetration in ordnance gelatin.

The hard wax may be more like plywood than water and favor a round nose more than a flat nose.

In water, the round nose is off course after only a third of the straight path of the FN.

Mixing water and wood seems a much fairer test to me, if you don't have dead elephants or dead buffalo to Texas-Heart-Shoot.

I'll give you the "Iron Buffalo" if you'll pay for the shipping.

1, 2, or 3 of the 7/16" thick plywood boards may be used between each bag of water:


One could pile all manner of material into one of these. Just make it the same for each shot. Reproducible. Consistent.

That is the benefit of artificial media over live or dead animals.

Each shot is different with dead buffalo or elephant. No consistency. A very large sample would be required for "statistical significance."

At least for the artificial media, a small sample is meaningful, due to the consistency in that media, whatever the media.

But some media favor a round nose, and some media favor a flat nose. Live and dead game favor a flat nose.

Maybe 9 feet of Bullet Test Tube?
Sure would be easier than filling those trash compactor bags with pond water.

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Not necessarily would different materials need to be used.

Surely a complicated proposition, but a design could be produced to give the same weight and length of bullet and same location of CG relative to front, by varying the length of the cavity and the taper of the cone and meplat size of the FN, with a purely hemispherical round nose. It could not be a purely cylindical FN, probably, but that is not necessary. I suspect the GSC FN shape would be very close to perfect.

Same material and thickness of the sidewalls of the skirt at base cavity ought to be maintained, I reckon, but the length of the cavity could be tuned to vary the CG, weight, and overall length of the bullets to get them to match. Triple variables to match up.

It would require computer assisted design the likes of which Walterhog may not be capable of, and Gerard has crocodiles rising from knee level to hip level as busy as he must be getting.

Sumbuddy good at using calculus to model bullet material volume measurements on dart bullets?