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Usmc To Buy Polymer-Cased Ammo


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#1 Dawes

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Posted 05 April 2019 - 0926 AM

So is plastic cased ammunition finally ready for prime time?

 

https://www.thefirea...bre-ammunition/


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#2 TTK Ciar

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Posted 05 April 2019 - 2059 PM

Trying to figure out which polymer they're using sent me down an hours-long rabbit-hole.

Judging from MAC LLC's patents, looks like it might be a 15/85 blend of PPSU (Radel) and plain old polycarbonate.

Strength, stiffness, thermal insensitivity and ductility are all important, but it's surprising a polymer that weak is suitable (about 9000 psi tensile strength).

I suppose all it has to do is seal the chamber seams during firing and then survive extraction, and there's a metal base to help with extraction, with the polymer case nested deeply into it, with gripping thread.

Edited by TTK Ciar, 05 April 2019 - 2059 PM.

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#3 GregShaw

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Posted 05 April 2019 - 2246 PM

All that really matters is the case head doesn't split, and the body obdurates the chamber. As long as the shooter doesn't get a facefull of gas, and the bolt face doesn't get gas cut, the case has done its job. I'd be more concerned about the thermal properties, is it more likely to cookoff? is it an effective heat sink to remove heat from the chamber, or a good insulator to keep the heat out of the chamber in the first place.


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#4 TTK Ciar

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Posted 06 April 2019 - 0022 AM

Good insulator, lousy heatsink.
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#5 GregShaw

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Posted 06 April 2019 - 0708 AM

Good insulator, lousy heatsink.

What I assumed. Probably a good combination for reducing cook offs.


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#6 shep854

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Posted 06 April 2019 - 0725 AM

I wonder how they avoid case-head separation in hot/dirty guns.


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#7 sunday

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Posted 06 April 2019 - 0814 AM

From my lack of deep understanding on the matter, as the program is for 12.7x99mm, .50 cal ammunition, there is a big potential to reduce weight because it is a large round, and less possibilities of cook offs when firing from an open-bolt machine gun. Also, there is about an inch of brass in the cartridge head. It is remarkable that the ejected cartridges are not so hot, according to the video. Seems the polymer avoid heat transmission to the chamber.

 

Perhaps they used PC for strength, and the PPSU is intended to provide temperature resistance.

 

Probably aluminium is a better solution for 20mm, and up, calibers.


Edited by sunday, 06 April 2019 - 1342 PM.

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#8 Dawes

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Posted 06 April 2019 - 0905 AM

The A-10 has always used aluminum-cased 30mm (quite successfully).


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#9 Panzermann

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Posted 06 April 2019 - 0909 AM

The A-10 has always used aluminum-cased 30mm (quite successfully).

 

As have many other aircraft guns. But I doubt you can use aluminium in the M2 or M3 machineguns.

 

I guess this plastic ammo is first going to helicopters?


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#10 GregShaw

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Posted 06 April 2019 - 1503 PM

CCI has made aluminum cased handgun ammo (CCI Blazer) for about 30 yrs. Didn't seem to be full powered, and Winchester White Box or Remington UMC wasn't much more expensive and reloadable as well. Big difference between loading a handgun case to 20k psi, and a rifle cartridge to 50k psi +. I don't know of anyone loading AL to .223 pressures, much less 5.56 lvl.


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#11 shep854

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Posted 06 April 2019 - 1650 PM

Be it noted that the M2 is a closed-bolt gun, like the old .30s.
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#12 sunday

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Posted 06 April 2019 - 1729 PM

Be it noted that the M2 is a closed-bolt gun, like the old .30s.

 

Oops...


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#13 Adam Peter

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Posted 08 April 2019 - 0957 AM

I idly wonder they go plastic as the anti-small plastic sentiment is rising, while they are trying to avoid lead in the name of Environment Protection...


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#14 TTK Ciar

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Posted 08 April 2019 - 1748 PM

It takes a few years for mainstream stupidity to find its way into the military procurement process.
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#15 Chris Werb

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Posted 10 April 2019 - 1224 PM

Being anti tossing endless small plastic items into the environment isn't stupidity, it's common sense.


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#16 TTK Ciar

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Posted 10 April 2019 - 1231 PM

So stop tossing them into the environment. Denying our civilization the use of some of the most useful materials in history is not the right solution. Keeping waste plastic out of the ocean shouldn't be that high a bar to reach.
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#17 DB

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Posted 13 April 2019 - 0646 AM

And it's not us doing it, in the main. Some statistics suggested that Chinese rivers were dumping in tonnes what ours were in kilogrammes.


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#18 shep854

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Posted 13 April 2019 - 0659 AM

And it's not us doing it, in the main. Some statistics suggested that Chinese rivers were dumping in tonnes what ours were in kilogrammes.

India, too.  For less-developed regions, the use of large rivers for garbage disposal is a given.  For the locals, there are more important things.


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#19 seahawk

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Posted 13 April 2019 - 0703 AM

Door gunners will like it. More ammo for the same weight and not hot brass flying in your face.


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