renatohm said:

Armies seem to agree more with 'my' definition...

Can you name any armies that issue PDWs to cooks, clerks, or other REMFs?

I've seen German tankers with Uzi SMGs, Polish tankers with wz63 SMGs, Russian pilots with APS machine pistols, Dutch pilots with MP9 SMGs, German and American special forces with MP7 SMGs, American pilots with GAU-5A carbines.  All are combat personnel.

I have yet to see cooks or clerks armed with any of those PDWs.

AM I THE ONLY ONE WHO IS INTERESTED IN HOW THIS THING SUPPOSED TO WORKS??

I'm trying to figure out how the internal mechanism works, if the chamber is on top of the magazine then how does the hammer, assuming it was in the bottom of the mag, can reach the firing pin, or does this thing use striker mechanism?

Kel-tec P50 pistol fired - YouTube

The NEW Kel-Tec P-50 5.7x28mm Pistol #GunFest2021 - YouTube

I wonder if a variation of the SS90 with this specs:

* < 22 grains

* front plastic core, tip exposed

* steel base

* Vo > 900 m/s

Would deliver enough quickly energy after impact against an unprotected target in order to create much bigger temporary wound channel and maintaining a P90-sized-and-weight type PDW controllable by a not so much trained user

what do you think?

I have no idea how to predict the terminal behavior of a hypothetical projectile.  I think it would be necessary to manufacture a quantity of such bullets, load them into cartridges cases, and fire them into ordnance gelatin, to see what wound channel they would produce.

poliorcetes said:

I wonder if a variation of the SS90 with this specs: * < 22 grains * front plastic core, tip exposed * steel base * Vo > 900 m/s Would deliver enough quickly energy after impact against an unprotected target in order to create much bigger temporary wound channel and maintaining a P90-sized-and-weight type PDW controllable by a not so much trained user what do you think?

Problem is likely penetration in flesh / ballistic gelatin.

The 27gr SS195/SS198 projectile used in the current 5.7 loads never seems to penetrate more the ~9". Thats even with impact velocities exceeding 2400fps. 

https://www.youtube.com/watch?v=q8YylhQWcpE

Once you get to 32-40gr, it starts to easily make 12" of penetration. 

https://www.youtube.com/watch?app=desktop&v=fsQoP3pZnDI

Now, some could argue that the 12" penetration minimum established by the FBI was for handgun projectiles, and that due to the 'rifle like effects' of rifle rounds, 12" is not necessary. I generally would fall into that category for a larger round (ie a fragmenting 7.62x51 that penetrates 10" is likely plenty effective.)

But for military adoption, I think their unlikely to go for any round that doesn't make the 12" penetration, as thats become such an ingrained metric. 

gatnerd said:

Thats a full size rifle with trained infantry shooters, firing not under serious stress (ie no one was trying to kill them.) Trying to make a 300m PDW, when full size Assault Rifles are already only 0.3 effective at 300m, seems dubious. Especially when you consider that the PDW equipped soldier has both less training and less shooting-combat experience then a typical rifleman. And of course it faces the brutal PDW paradox - the closer the PDW becomes in performance to a rifle, the more it begins to carry like a rifle due to increases in size and weight. At which point, why are they not carrying rifles? Or carrying a rifle caliber PDW (SBR ala Krinkov, etc.)

Hmm, 2 points here

1. How would this change with sights?
2. I am not sure I agree with the rifle approximation thing. The P50 could be made to fire my round, which is a shortened Grendel to 25mm and a bullet with a 15mm ogive. COAL is 40mm or .5 mm shorter than 5.7. Muzzle energy is around 1500J or 1100 ft lbf. That is fundamentally rifle performance akin to the 5.45 Russian. This from a 9.6" barrel. Muzzle pressure is ~80 MPa, so loud, but not ear(th) shattering. Recoil pretty massive at 8.8 ft lbf without moderator or muzzle brake. This is about the same recoil as a .357 Magnum from a revolver or 5.56 from a rifle. Even without a stock and just with a front grip this should be doable. FA might be challenging without a shoulder stock though ;)

So this thing would be bulky, since the mag would have to be thicker, but otherwise? Should carry like a 44 Magnum and shoot nicer.

I get that 300m might be pushing it, but in competent hand it could do it and otherwise it's a nice powerful cartridge for shorter range.

stancrist said:

Can you name any armies that issue PDWs to cooks, clerks, or other REMFs? I've seen German tankers with Uzi SMGs, Polish tankers with wz63 SMGs, Russian pilots with APS machine pistols, Dutch pilots with MP9 SMGs, German and American special forces with MP7 SMGs, American pilots with GAU-5A carbines. All are combat personnel. I have yet to see cooks or clerks armed with any of those PDWs.

I'd submit that this is not least due to there not being a good one. I also think that thinking may yet change when we move back to full power battle rifles in some kind of 6.8 Magnum

1. How would this change with sights?
2. I am not sure I agree with the rifle approximation thing. The P50 could be made to fire my round, which is a shortened Grendel to 25mm and a bullet with a 15mm ogive. COAL is 40mm or .5 mm shorter than 5.7. Muzzle energy is around 1500J or 1100 ft lbf.

1. The ACR trials tried an M16 with 4X ACOG, and only showed a slight increase in hit probability at long range. At intermediate range there was almost no difference.

2. The P50 is direct blowback, so there is no way to have it work with a 1100ft/lb cartridge. 

Ultimately anything firing a rifle powered cartridge is going to end up being rifle weight and length. You'd get some savings in length using a magazine in grip format, but weight savings would be minimal.

The MP7 is 4.2lbs firing the 350ft/lb 4.6, using the magazine in grip format. Its unlikely this cartridge of yours - substantially more powerful - would end up in a equal or lighter format.

And of course, even if you did, you'd then kill off one of the main PDW advantage the MP7/P90 affords - extreme controllability that allows a novice shooter to use the weapon easily.

gatnerd said:

2. The P50 is direct blowback, so there is no way to have it work with a 1100ft/lb cartridge. Ultimately anything firing a rifle powered cartridge is going to end up being rifle weight and length. You'd get some savings in length using a magazine in grip format, but weight savings would be minimal. The MP7 is 4.2lbs firing the 350ft/lb 4.6, using the magazine in grip format. Its unlikely this cartridge of yours - substantially more powerful - would end up in a equal or lighter format. And of course, even if you did, you'd then kill off one of the main PDW advantage the MP7/P90 affords - extreme controllability that allows a novice shooter to use the weapon easily.

I am more thinking a P50 inspired weapon with delayed blowback, firing from a closed bolt. And I dispute your claim that a rifle powered cartridge will lead to a rifle length and weight weapon. I really think the P50 layout offers a way out of that.