Military Guns and Ammunition

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armour piercing ammunition   Ammunition <20mm

Started 28-Dec by graylion; 3007 views.

From: smg762


With energies of roughly 1000ft lbs,  a 19.  Caliber would have by far the best energy retention at 300m.  A 6mm wouldn't come close.  

If penetration must be extreme,  you'd want a fairly 'full' shaped bullet,  closer to 556 shape than modern,  pointy,  VLD shapes.  This would allow an extremely large steel core,  which is far more economical than tungsten. 

Finally though,  slimmer calibers do struggle in short barrels,  energy wise.  Because the swept volume is less. 

A mars-style round would need at least 19 inches of barrel to reach 1300jouls,  if the caliber was. 19 (5mm)

Your PDW should therefore be a bullpup,  which uses reverse feeding (like the boberg pistol) to shortern the overall length.   Lastly,  you'd want the magazine right at the very rear of the bullpup.... far away from the grip (again this shortens length).... also,  don't use a flash hider.  That would add an inch of length. 

Ultimately you can get extreme 300m penetration with far less energy.  An. 18 caliber,  with about 750 ft lbs and a steel core,  would do the same job.  From a 15inch barrel. 


From: graylion


I am going for something that can be carried in a thigh holster - like the Keltec gun we are discussing in the other thread. 

Where I am at is this bullet:

which with my cartridge gives me 1417 J aka 1198 ftlb at a V0 of 2755 ft/s. At 300 yds it retains 2031 ft/s at an energy of 651 ftlb. This is from a 10.5" barrel, using drive bands. 

What concerns me is the muzzle pressure of 13.500 psi.

  • Edited 29 December 2020 8:34  by  graylion

From: smg762


The keltec gun could never work in thigh holsters.  The magazine is extremely wide... and that means the gun is too. 

If it must be holsterable,  you want a gun with the magazine in the grip.... like an MP7. 

to get acceptable energies you'd need a cartridge that resembles a fat 10mm/. 45,  necked down to small caliber.  The grip needs careful design to remain comfortable.  You could just about get a mars-sized round but it would be shorter and fatter than the mars. 

1100ft lbs from a 10 inch barrel is completely impossible with a mars sized round. Swept volume plays a massive role.  You'd need a 7. 62 bullet to get that kind of short barrel performance. 

The mars had 830 ft lbs from a 10 inch barrel - and it still had pressure problems. 

Also,  6mm @ 1100 ft lbs would not be  Pleasant or controllable in a light holsterable thigh gun.  even from a 3kg M4 carbine the felt recoil would exceed 556.  

My suggestion (for a holster carbine)

MP7 style weapon with 11. 5 inch barrel.  Uses boberg-style reverse feeding.  And the grip/mag is set very far back,  just like the prototype MP7 (Google it). 

Stock is side folding to reduce length. Total length matches the MP7 

Caliber is basically a 10mm or. 45 sized round,  necked down to. 20 caliber.  Far more controllable. Energies of 850ft lbs are recommended,  with heavy 47 grain bullets. 

  • Edited 29 December 2020 9:20  by  smg762

From: gatnerd


graylion said:

so I am fundamentally thinking a hardened steel core like the 855A1 in a 1300J PDW round (modernised version of 5.56x30 MARS)

Chinese Level IV bought for less then $100 per plate on Aliexpres is stopping M2AP fired at 3000fps+ from a .300 Win Mag from 45' away. Its stopping 7.62 M993 Tungsten at 2750fps impact velocity. Its stopping .338 Lapua Tungsten from 200yds...

The point being that any rifle round, much less PDW round, is no longer really armor piercing against hard torso armor. AP is only relevant for a PDW in terms of penetrating the IIIA helmet. 

I suggest checking out Buffman's youtube channel for a look into what modern armor can handle.


From: dobrodan


If I had been a REMF, I would have loved something like the KelTec SU-16 C with a 12 inch barrel, with a small suppressor, and carried it in a holster, stock folded, with a 20 round magazine.

It is light, compact, cheap, and easy to maintain, while using the same ammunition and magazines as the M-4/M-16.


  • Edited 29 December 2020 13:38  by  dobrodan

From: graylion


this is a public quickload equivalent on the Geoffrey Kolbe website. Loud, yes. For recoil control, I'd try balanced recoil.  I like the idea of basing it on 10mm Auto or .45 - I have thought about that myself. My mind currently is on a neckless polymer cartridge.

As for small calibre - would making the penetrator thinner not have the same effect?

Oh and why is carrying a 2" wide gun in a thigh holster impractical? The drum of a .44 is easily that size?

I like the gun layout you are proposing. I am not sure one can make a handle for a cartridge with a 10mm kind of case and a 10mm ogive that can be used by small female shooters.

47gr copper/steel bullet in .17 and a big pistol case fundamentally goes down all the way to the primer

BTW tungsten is not feasible. It is both highly toxic and mass production would take up significant percentages of the Western output

  • Edited 29 December 2020 14:50  by  graylion

From: smg762


You could have a slim penetrator in a 6mm round but again it would have twice the recoil,  and half the range of a. 20 cal round.  (. 20 is very different from. 17)

Any gun using a P90 magazine (like the keltec PDW) will be well over 2. 4  inches wide.  Carrying it would be awful.  

An MP7 style gun could easily be 0. 9 inch,  which is insanely slim. 

The round I'm suggesting would resemble the. 225 jaws or the 224 boz.  Google will show u what they look like. 

It doesn't need to be larger than that,  or feature a long ogive.  Not with a 300m intended range. 

Grip comfort is not a problem for female shooters if u design the grip so it has a very small grip circumference. 

Ideal weight with the 11. 5 barrel,  is about 2.3kg unloaded.  


From: nincomp


gatnerd said...

The point being that any rifle round, much less PDW round, is no longer really armor piercing against hard torso armor. AP is only relevant for a PDW in terms of penetrating the IIIA helmet. 

In other words, they had it right in the StarGate television show. Use a P90 like a fire hose and hope to hit an unprotected area.


From: RovingPedant


An Armour Piercing Composite Rigid (APCR) is a pretty good compromise for use against armoured and unarmoured targets. I think that Tony has written about that sort of thing. The Russian 9mm had a composite AP projectile apparently.

Steel over tungsten for the core though. Aluminium or polymer “sabot”. Bonus points for making it biodegradable.


From: smg762


The VBR PDW used this too.  9mm necked down to 762,  with a steel insert.  It's poor beyond 50-100m,  because the B.C. is no better than 9mm