US Army Signs High-Performance Ammunition Agreement with Federal

Yes - all of that extra energy has to be dissipated somehow. I haven't read much about how that is set up to work. It can't just be stiffer springs. Action/re-action makes me wonder how much of it is going into the shoulder of the shooter?

A large amount of that is dependent on the interface of the cartridge case with the chamber. An original M16 with proper case hardness M193 ammunition would actually run without an extractor as the case "rebounded" from the chamber walls while there was still residual pressure (about 5-8000psi) in the throat area so the case would be blown out of the chamber by that gas. This type of high energy round will put more "pressure", so to speak, on firearm manufacturers to build better guns and more consistent guns. If you see a rifle "ripping" a case out of the chamber you have some other issues at work, mainly the culprit is likely to be a soft case (unless you are in a type of G3 style blow back then all bets are off) and you are seeing physical sticking of the case in the chamber when it should have rebounded and come free. Brass yields and permanently deforms in most rifle cartridges as reloaders know. The amount of permanent deformation is determined by the yield point, the lower it is (soft) the more permanent deformation and the greater chance of sticking. When you apply even higher pressures you need to look at the yield point of the case and see how much "help" the chamber is getting in containing the pressure and do your deformation analysis from there. It is much easier in commercial non-auto firearms as we do not cycle at 10+ times per second so residual pressure is functionally zero and a lot of this never shows up in our world of hunting and paper punching or even self defense. Its a very interesting project and a pretty inexpensive way of life extending designs IF the guns can handle it. I got the popcorn popping, it's been an interesting watch so far.

Full disclosure, I have spent a career in military small arms and at one point I tested Canadian C7 and C8 configuration rifles on a steady diet of proof rounds (SNC/IVI proof at the time ran from 80k to 100k psi on the pressure barrel) and the Diemaco guns had no issues. I can also say that Canada made over 100 significant changes, refinements, and clarifications to the original M16 TDP we licensed before it was approved as our service C7 rifle TDP. These were a lot of the reasons behind why the Netherlands, Denmark, and the UK SF community (SAS et al) selected the Canadian rifle over less expensive alternatives. The US will need to pay a lot more attention to material, heat treatment, and finish quality of the pressure containing parts of each nominated weapon's system. The fact that the US military does not expect the service life that other countries do plus you alone are able to buy the volumes you do and replace things on a much more aggressive schedule will contribute much to the future success of this type of enhancement. Canada runs it's rifles for basically a career soldier's career so 25 to 30 years, now approaching 40 years (we issued starting in 1988 and still going with 2 major overhauls/configuration changes - A1 flat top, A2 adjustable length butt). The US used to plan to get 7 to 10 years out of a rifle. These are factors that other countries looking at these types of cartridges will need to factor in.