Military Guns and Ammunition

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This is intended for people interested in the subject of military guns and their ammunition, with emphasis on automatic weapons.

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modified 5.7x28   General Military Discussion

Started 10/1/23 by smg762; 2181 views.
In reply toRe: msg 1

From: JPeelen


You are simply replicating the "pencil" type of long thin cases from the late 19th century, which became notorious for being ballistically inefficient. I other words, low muzzle energy per gram of propellant due to geometry against the laws of thermodynamics.   

If you only studied more closely the history of small arms and small arms ammunition, you could avoid proposing scheme after scheme that has been tried decades (if not a century) ago and turned out to have drawbacks that make it impractical.

  • Edited 10 January 2023 16:21  by  JPeelen
In reply toRe: msg 1

From: roguetechie


You're basically trying to reinvent the knoxx HEC which was a military development project to essentially make a straight wall very high pressure 5.56 that got equivalent or better performance to existing 5.56.

Knoxx was fairly close to succeeding, except for the occasional round that would have a wild "pressure excursion event" (300k psi plus near as they could tell) and blow up their mann test actions lol.

Could you do something like that these days?

I tend to think that if you couldn't you could get extremely close.

Also, for the billionth time foot pounds of energy is a trash metric for any sort of performance determination, stop using it.


From: Farmplinker


TBF, some older ideas might actually work now with modern materials and manufacturing techniques. 

Although I think Emeric's neckless case experiment is more likely to work than the one in the OP.


From: smg762


ok ii've modified it. Total length is 67mm.   Scratch built case, with base diameter 8.3mm.  (wider than 5.7)

bullet is a 6.5mm FABRL, which is only 34mm long.  Case preassure 75k. 

could 1800 ft lbs be reached?

could you hollow out the base of the bullet to add more powder?

Also, could you squeeze in a .30caliber sabot, if the neck was extremely thin....  i feel this would be the boost needed to reach 1800ft lbs

  • Edited 11 January 2023 10:05  by  smg762

From: roguetechie


Emerics neckless brass case stuff is pretty exciting.

I do very much agree on older concepts becoming viable too. I think that our next round of material improvements is likely already possible and just waiting for someone to dust off an older concept that didn't work previously and update it.

On this note, Caleb crye's 5.56 or 300 bo feed through pistol grip concept is probably one of those things that just needs cleaned up and to have already existing innovation from outside the gun world applied to it to make it viable.

In reply toRe: msg 7

From: roguetechie


Why 6.5 fabrl?

Also when you scaled up bullet diameter you made sure to equally scale up projectile length with it right?

Otherwise your "6.5 fabrl" won't have the same performance characteristics your idea seems to need.


From: Gr1ff1th


Gatnerd, do you mean QuickDesign or QuickLoad, because I have QuickLoad, send me the cartridge specs and I'll run them 


From: smg762


in terms of handling high pressures, aren't big game cartridges often straight walled?

would such a cartridge extract realiably?


From: Farmplinker


Er, no. The straight-wall cases are for lower pressure rounds, generally. Those Nitro Express cartridges were big to keep pressures low enough for break-open rifles.


From: smg762


emeric i had a question...

i've modified the parameters of the round - it's now much more powerful.

caliber is .25, so the bullet diameter is 6.49mm (not 6.7mm)

ME is 2100ft lbs - similar to a hot 6mm cartridge

base diameter is much wider now - but still far slimmer than typical 6.5mm rounds

it's 9.85mm - slightly wider than 556.

case is about 49mm tall, and the CETME bullet is almost entirely outside the case - there's about 4-5mm of bullet in the neck.

do you think it would work, and would it reach the target energy?

and i wanted the bullet to be entirely hardened steel. could such a bullet reach a reasonable weight?  idieally 95 grains