autogun

Military Guns and Ammunition

Hosted by autogun

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

  • 3218
    MEMBERS
  • 182855
    MESSAGES
  • 4
    POSTS TODAY

Discussions

PDW again   Small Arms <20mm

Started 20-Dec by DavidPawley; 31528 views.
Red7272

From: Red7272

3-Feb

roguetechie said:

That's kinda the whole point here, no amount of rearranging the deck chairs on the titanic of convention small cartridge design is going to give you the performance we want or that cartridge and loading would already exist.

Yup 9x19  +P+ and 5.7x28 are the two ends of the spectrum. There really is no point to adding  a third indifferent round with limited lethality. Increased OAL for the 9x19 for a pointed steel projectile might be interesting but not enough that anyone has actually done it. Even the Russian 7N21 has a round point despite being a dedicated AP round. Probably to promote feeding with a more-or-less straight cased round. 

stancrist

From: stancrist

3-Feb

roguetechie said:

...no amount of rearranging the deck chairs on the titanic of convention small cartridge design is going to give you the performance we want...

Is that the royal "we" or do you have a mouse in your pocket?   8^)

There are diverse opinions here about what performance a PDW should have.

graylion

From: graylion

4-Feb

Red7272 said:

roguetechie said: That's kinda the whole point here, no amount of rearranging the deck chairs on the titanic of convention small cartridge design is going to give you the performance we want or that cartridge and loading would already exist. Yup 9x19  +P+ and 5.7x28 are the two ends of the spectrum. There really is no point to adding  a third indifferent round with limited lethality. Increased OAL for the 9x19 for a pointed steel projectile might be interesting but not enough that anyone has actually done it. Even the Russian 7N21 has a round point despite being a dedicated AP round. Probably to promot:e feeding with a more-or-less straight cased round. 

I agree. I'd like a more powerful round that actually is a carbine round and not a pistol one. A combination of several technological advances gives the option of doing that:
 

  • modern powders, allowing faster combustion and shorter barrels
  • the understanding of combustion, leading to short and thick cartridges allowing shorter barrels
  • higher cartridge pressures
  • polymer or hybrid casings for even higher pressures  
  • the P90 style mag

this allows for a much smaller cartridge than .30 carbine to have similar E0 and be able to be used in a ridiculously huge "pistol" that can be turned into a carbine/SBR by virtue of a folding or detachable stock.

  • Edited 04 February 2021 9:49  by  graylion
graylion

From: graylion

4-Feb

stancrist said:

Is that the royal "we" or do you have a mouse in your pocket?   8^) There are diverse opinions here about what performance a PDW should have.

A lion ;)

Let's say 9mm has ~500J and the new 6.8mm Magnum somewhere north of 3kJ. A carbine round that sits between 1 and 1.5 kJ would seem to be sensible. 

stancrist

From: stancrist

4-Feb

graylion said:

Let's say 9mm has ~500J and the new 6.8mm Magnum somewhere north of 3kJ. A carbine round that sits between 1 and 1.5 kJ would seem to be sensible.

It does not seem sensible to me to set a purely arbitrary figure for muzzle energy.  What I think would be sensible is to decide what performance is wanted, then design the gun and ammo to achieve that performance.

graylion

From: graylion

4-Feb

stancrist said:

It does not seem sensible to me to set a purely arbitrary figure for muzzle energy.  What I think would be sensible is to decide what performance is wanted, then design the gun and ammo to achieve that performance.

point. So what do we want. Penetrate a IIIa helmet at what - 200m? 150?

Msg 7776.190 deleted
JesseH1234

From: JesseH1234

4-Feb

stancrist said:

It does not seem sensible to me to set a purely arbitrary figure for muzzle energy. What I think would be sensible is to decide what performance is wanted, then design the gun and ammo to achieve that performance.

Plus 1-1.5kj is just about the range of 5.45 and 5.56, the lower end out of particularly short barrels.  Also any ultra 9mm or uber-toke is still going to have cartridges similar in weight and bulk to 5.45 and 5.56.

Normally I don't like high pressure cartridges for military applications, due to the barrel heating and weapon battering; I suspect there is a reason wartime German and modern Russian and Chinese cartridges operate in the low 40k psi range generally. 

However, for the stated purpose of a PDW, I think the 5.7 kind of nailed things; you get a meaningful reduction in cartridge weight, increase in capacity, and capable of being fired out of a very light weapon.  And the high pressure will not matter much, because these things by definition aren't being actually shot all that much.  It's flat shooting, stays supersonic for 300-400m (I think).  While it's no elephant gun, anything short of 30-06 will have some "stopping power" complaints.

I liked Tony's idea a while back, which assuming I am recalling correctly (although maybe I am embellishing a bit) was basically a FiveSeven with a detachable stock of some kind.  Add a 7-8" barrel (to get most of the cartridge potential), a small flash hider, and a small red dot in a holster that fits it, and I bet you could get a nifty little package.  Which, along with a decent amount of ammo, say 100-120 rds, would still probably weigh 2kg or less total. 

Otherwise, 5.45 is pretty efficient out of a 12-13" barrel, and ak stocks can fold.....

stancrist

From: stancrist

4-Feb

graylion said:

So what do we want. Penetrate a IIIa helmet at what - 200m? 150?

Well, if we're talking about a PDW to equip non-infantry in a 6.8 NGSW future, and since NGSW is meant to defeat Level IV body armor, shouldn't the PDW also be able to punch through Level IV armor?  Not out to the extended (600 meters) range of NGSW, of course, but at the shorter engagement distances likely to be encountered by rear echelon troops, say 100 meters or so.

stancrist

From: stancrist

4-Feb

JesseH1234 said:

...for the stated purpose of a PDW, I think the 5.7 kind of nailed things...

5.7 does have some desirable aspects, but it was created before the proliferation of Level IV body armor became an issue.

TOP