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PDW again   Small Arms <20mm

Started 20/12/20 by DavidPawley; 101673 views.
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
stancrist

From: stancrist

10/2/21

graylion said:

I assume you agree on mag on top of action/barrel, not the other way 'round?

Yes.

graylion said:

I am going to postulate a folding down front grip.

Okay.

graylion said:

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?

Not an area in which I have knowledge.  Suppressor does not appear to reduce recoil in this video:  https://youtu.be/qY-IuDabD3Q?t=5

graylion said:

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

Okay, although I think that likely does not matter.  Any armies which were to adopt it, might very well specify a different selector pattern.

stancrist

From: stancrist

10/2/21

smg762 said:

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?

I don't know that I'd call it "reasonably good", but it's perhaps good enough to be usable.  Doesn't seem like any armies like 6.5 CBJ enough to adopt it, however.

  • Edited 11 February 2021 0:38  by  stancrist
graylion

From: graylion

11/2/21

stancrist said:

Not an area in which I have knowledge. Suppressor does not appear to reduce recoil in this video: https://youtu.be/qY-IuDabD3Q?t=5

They do because of gas expansion, see here https://youtu.be/h4ESNfY1SuU

I think there should be some solid amount of expansion space next to the barrel, but even an integrated suppressor is making the gun longer, so I think we can forgo that. Muzzle brakes also make the gun longer and they increase the noise for the guys who are fighting next to you. We may have to simply not use any of this. Bang is actually not too bad (like a heavy handgun, less than a 5.7 handgun) and recoil is somewhere along the lines of 5.56x45. Would that be OK with our frame?

I am going to postulate the Boberg principle since it basically shortens the gun by a full cartridge length. Roller delay and closed bolt affect reliability and precision, Same mechanism as MP5 and G3, so I'd like these 2. I could not find anything about the Boberg principle being unreliable, OTOH it has never been used for full auto before. Given that the PDW replacement is not urgent, the Elbonian Office for Arms Procurement decides on an extended trial.

  • Edited 11 February 2021 9:03  by  graylion
stancrist

From: stancrist

11/2/21

graylion said:

I think there should be some solid amount of expansion space next to the barrel, but even an integrated suppressor is making the gun longer, so I think we can forgo that. Muzzle brakes also make the gun longer and they increase the noise for the guys who are fighting next to you. We may have to simply not use any of this. Bang is actually not too bad (like a heavy handgun, less than a 5.7 handgun) and recoil is somewhere along the lines of 5.56x45. Would that be OK with our frame?

Seems reasonable to me.

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