12-13-2020, 04:00 AM
grayfox Wrote:To get that kind of MV/KE they are talking about, way back I said they'd need ~80ksi... looks like that's where they're going.
And this is AFTER the Army reduced the velocity requirements. I ran the numbers a while back and they basically wanted the performance of a 270 WSM (from its 23+inch barrel) to come from a carbine with roughly a 13 inch barrel. From what I remember, Sig fudged its "cartridge weight reduction" number by comparing its weight to what a comparable cartridge WOULD have been, instead of comparing it to the weight of the existing 7.62 NATO ammo.
The General Dynamics design is a bullpup in order to keep a longer barrel for the same weapon length and permit them to run lower chamber pressures than the other two. The interesting part of its cartridge is that it was optimized from the beginning for a polymer case. In other words, it isn't shaped like a brass or steel case. Most previous attempts with polymer just tried to replace the existing brass case with no other design changes.
Textron has been working on case-telescoped ammo for decades. I am not certain if tucking the bullet into the case is worth all the trouble of an entirely new type of action. At least the General Dynamics cartridge can use a traditional action.