Dawes Posted April 5, 2019 Share Posted April 5, 2019 So is plastic cased ammunition finally ready for prime time? https://www.thefirearmblog.com/blog/2019/04/04/usmc-to-by-2-4-million-rounds-of-polymer-cased-50-calibre-ammunition/ Link to comment Share on other sites More sharing options...
TTK Ciar Posted April 6, 2019 Share Posted April 6, 2019 (edited) 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 April 6, 2019 by TTK Ciar Link to comment Share on other sites More sharing options...
GregShaw Posted April 6, 2019 Share Posted April 6, 2019 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. Link to comment Share on other sites More sharing options...
TTK Ciar Posted April 6, 2019 Share Posted April 6, 2019 Good insulator, lousy heatsink. Link to comment Share on other sites More sharing options...
GregShaw Posted April 6, 2019 Share Posted April 6, 2019 Good insulator, lousy heatsink.What I assumed. Probably a good combination for reducing cook offs. Link to comment Share on other sites More sharing options...
shep854 Posted April 6, 2019 Share Posted April 6, 2019 I wonder how they avoid case-head separation in hot/dirty guns. Link to comment Share on other sites More sharing options...
sunday Posted April 6, 2019 Share Posted April 6, 2019 (edited) 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 April 6, 2019 by sunday Link to comment Share on other sites More sharing options...
Dawes Posted April 6, 2019 Author Share Posted April 6, 2019 The A-10 has always used aluminum-cased 30mm (quite successfully). Link to comment Share on other sites More sharing options...
Panzermann Posted April 6, 2019 Share Posted April 6, 2019 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? Link to comment Share on other sites More sharing options...
GregShaw Posted April 6, 2019 Share Posted April 6, 2019 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. Link to comment Share on other sites More sharing options...
shep854 Posted April 6, 2019 Share Posted April 6, 2019 Be it noted that the M2 is a closed-bolt gun, like the old .30s. Link to comment Share on other sites More sharing options...
sunday Posted April 6, 2019 Share Posted April 6, 2019 Be it noted that the M2 is a closed-bolt gun, like the old .30s. Oops... Link to comment Share on other sites More sharing options...
Adam Peter Posted April 8, 2019 Share Posted April 8, 2019 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... Link to comment Share on other sites More sharing options...
TTK Ciar Posted April 8, 2019 Share Posted April 8, 2019 It takes a few years for mainstream stupidity to find its way into the military procurement process. Link to comment Share on other sites More sharing options...
Chris Werb Posted April 10, 2019 Share Posted April 10, 2019 Being anti tossing endless small plastic items into the environment isn't stupidity, it's common sense. Link to comment Share on other sites More sharing options...
TTK Ciar Posted April 10, 2019 Share Posted April 10, 2019 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. Link to comment Share on other sites More sharing options...
DB Posted April 13, 2019 Share Posted April 13, 2019 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. Link to comment Share on other sites More sharing options...
shep854 Posted April 13, 2019 Share Posted April 13, 2019 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. Link to comment Share on other sites More sharing options...
seahawk Posted April 13, 2019 Share Posted April 13, 2019 Door gunners will like it. More ammo for the same weight and not hot brass flying in your face. Link to comment Share on other sites More sharing options...
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