gatnerd

Military Guns and Ammunition

Hosted by gatnerd

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

  • 3323
    MEMBERS
  • 188467
    MESSAGES
  • 13
    POSTS TODAY

Discussions

PDW again   Small Arms <20mm

Started 20/12/20 by DavidPawley; 98585 views.
graylion

From: graylion

9/2/21

stancrist said:

graylion said: Anyway, what other options? since we are developing the cartridge, we can go for a shorter COAL, but also, the bigger cartridge will make this weapon even higher. For a cartridge of the size and power you propose, the only other option I can see is a conventional SBR, which has its own dimensional issues.

For a cartridge of the size and power you propose, the only other option I can see is a conventional SBR, which has its own dimensional issues.

see, of that I am not sure. I recon I need ca 1.6cc cartridge volume. Back of the envelope says that can be done in a very chubby cartridge (which is good for combustion) which is no longer than 5.7x28, and has a base diameter of ~12mm. This could be used in P90 like mags or possibly singe stack mags - widening to double underneath the handle? Just throwing ideas out.

I'd use a polymer case. I am thinking about a very light bullet with a very pointy tungsten or tungsten/steel penetrator, maybe an aluminium body and copper drive bands and a 7N21-like construction regarding discarding the core. I can get this pretty fast (~3800 fps) but velocity drops quickly. At 150 yds we are down to ~3000 fps, which might still pierce armour. 

I agree, that a classic rifle layout as you show in your pictures is probably counter productive, I'd prefer the P50 layout. A bullpup layout has fundamentally the same problem.

OTOP if this can be done in a 5.7x28 more brutal version, I'd be tempted to go down that route

  • Edited 09 February 2021 11:44  by  graylion
smg762

From: smg762

9/2/21

I am sure something like 6.5 CBJ would work best. from 12' barrels it can group 13 inches at 300m. Is that reasonably good?

stancrist

From: stancrist

9/2/21

graylion said:

stancrist said: For a cartridge of the size and power you propose, the only other option I can see is a conventional SBR...

see, of that I am not sure. I recon I need ca 1.6cc cartridge volume. Back of the envelope says that can be done in a very chubby cartridge (which is good for combustion) which is no longer than 5.7x28, and has a base diameter of ~12mm. This could be used in P90 like mags or possibly singe stack mags - widening to double underneath the handle? Just throwing ideas out. I'd use a polymer case. I am thinking about a very light bullet with a very pointy tungsten or tungsten/steel penetrator, maybe an aluminium body and copper drive bands and a 7N21-like construction regarding discarding the core. I can get this pretty fast (~3800 fps) but velocity drops quickly. At 150 yds we are down to ~3000 fps, which might still pierce armour.

Perhaps it would work.  The trouble is, it's rather difficult -- for me, at least -- to really evaluate a gun and ammo that cannot be handled or fired.

However, I do like the basic concept of a PDW with P90-type magazine.  Similar weapons have been proposed before, but only in pistol calibers.

Italian "Bullpup" Submachine Gun Concept Unveiled, Futuristic Electronic PDW? -The Firearm Blog

Marshal Arms Pistol (securityarms.com)

graylion

From: graylion

9/2/21

stancrist said:

Perhaps it would work. The trouble is, it's rather difficult -- for me, at least -- to really evaluate a gun and ammo that cannot be handled or fired. However, I do like the basic concept of a PDW with P90-type magazine. Similar weapons have been proposed before, but only in pistol calibers. Italian "Bullpup" Submachine Gun Concept Unveiled, Futuristic Electronic PDW? -The Firearm Blog Marshal Arms Pistol (securityarms.com)

Yup, have seen the top one, not the bottom one. Are you willing to proceed on the basic assumption that P90 style mag works and we'll go talk about other details?

autogun

From: autogun

9/2/21

The Hill SMG of 1952:

stancrist

From: stancrist

9/2/21

graylion said:

Yup, have seen the top one, not the bottom one.

The Marshal Arms gun was about two decades ago.  I was very interested in PDW designs back then, so wrote an article about it after seeing his presentation in the 2000 NDIA Proceedings.  Had completely forgotten about it until now.  Apparently it never went any further.

graylion said:

Are you willing to proceed on the basic assumption that P90 style mag works and we'll go talk about other details?

Sure, go ahead.

  • Edited 09 February 2021 15:40  by  stancrist
graylion

From: graylion

9/2/21

stancrist said:

Sure, go ahead.

So next is layout. Given that we are talking about a rather powerful cartridge, the option of having the barrel over the magazine is considered and discarded, muzzle climb would simply be too high. The next question is stock. Several options present themselves

  1. swivel over the top.
  2. folding sideways
  3. detachable
    1. carried somewhere on the webbing
    2. rigid holster that doubles as stock
  4. Telescopic stock of the kind with two prongs that go either side of the gun

1 and 2 have issues with holstering, 3 in general has the problem of attaching the stock taking time (how much of an issue is this?)  3.1 trying to find the stock and 3.2 makes the holstered weapon even bulkier. 4 would appear to be the best solution at first blush. 

  • Edited 09 February 2021 19:23  by  graylion
stancrist

From: stancrist

10/2/21

graylion said:

So next is layout. Given that we are talking about a rather powerful cartridge, the option of having the barrel over the magazine is considered and discarded, muzzle climb would simply be too high. The next question is stock. Several options present themselves

1. swivel over the top.

2. folding sideways

3. detachable 3.1 carried somewhere on the webbing 3.2 rigid holster that doubles as stock

4. Telescopic stock of the kind with two prongs that go either side of the gun

1 and 2 have issues with holstering, 3 in general has the problem of attaching the stock taking time (how much of an issue is this?)  3.1 trying to find the stock and 3.2 makes the holstered weapon even bulkier. 4 would appear to be the best solution at first blush.

My take:

1 and 2 have issues with holstering only if you're talking about traditional holsters that cover most or all of the weapon.

IMO, for a weapon as large as your proposed PDW, a conventional holster is neither necessary nor particularly desirable.

I think that a much more abbreviated "holster" -- more of an open framework, really -- would be better suited to the task.

This would allow use of a top  or side folding stock, but I'd rule out the top folder if an optical sight is standard equipment.

3.1 and 3.2 are very undesirable, IMO.  Both require steady hands in order to grab and attach the stock with any semblance of speed.

When the user is under physical and/or emotional stress, his hands are numb from arctic cold, wet with rain, covered in mud or blood?

Here's video of a guy attempting to attach a holster stock, and botching it under ideal conditions:  https://youtu.be/h_En_DqkRoc?t=53

Compare that to an integral side folder https://youtu.be/2JXqXAYLJ4A?t=257 and telescoping stock https://youtu.be/vkzelAfhsvA?t=120

Personally, I agree with a telescoping stock being the best choice, if only because it can be easily designed to be adjustable for the LOP.

  • Edited 10 February 2021 13:34  by  stancrist
roguetechie

From: roguetechie

10/2/21

Skeleton holsters are definitely one potential way to go. One of the better ones at that I might add.

graylion

From: graylion

10/2/21

stancrist said:

Personally, I agree with a telescoping stock being the best choice, if only because it can be easily designed to be adjustable for the LOP.

OK, so we have that. I assume you agree on mag on top of action/barrel, not the other way 'round?

I am going to postulate a folding down front grip.

Action. Now here are a bucketload of options:

  1. simple blowback
  2. delayed blowback
  3. gas/piston

personally I lean towards delayed blowback, specifically roller delayed. simple blowback won't handle this kind of powerful cartridge. Gas is just too complex and clumsy for the gun design we are envisioning.

Kind of action:

  1. normal
  2. Boberg

Boberg would give us more useable barrel length, can it be made reliable enough?

This will likely be a rather rough cartridge. Can we do something to make shooting it less unpleasant like eg an integrated suppressor?

I am also thinking that we might want to have a 4 way selector and a burst mode, given the fact that with these troups we can probably not rely on proper trigger control

  • Edited 10 February 2021 16:56  by  graylion
TOP