Old idea in a new jacket
Ze Jermans already tried this, quite a while ago and indeed that was that G11, which didn't even need the jacket so that there wasn't even anything to expel left. Only just when they were ready to try it in the field, the wall fell down, they reunited, and to pay for that they cut lots of things including this. So, if the rednecks have been "working for some time on this", well, it got shelved a score or so years ago so it's about time they had something to show for their efforts.
<hat type="tin foil">So, who really did bring down the wall? The americans of course, because the G11 threatened the M16 and the 5.56x45. Why else? They stuck to that effigy even when it failed to work in dirty environments like, oh, Vietnam.</hat>
So, alright, you've made some "progress" and dug up half of an old idea. Now do it again in bullpup configuration and save some more weight and length. There's your lightweight carbine SAW. Do we have to tell you everything? Sheesh.
Perhaps not obvious to European readers, but lots of small arms related claims and decisions are actually based on personal opinions held to be more dear, perhaps, than religious beliefs, and the debates do have plenty of the flamefest nature. That goes for almost every aspect; rifle calibre (eg the .280 that landed by the wayside), like whether or not to use the bullpup configuration (there's more than one "discussion" out there full of "hard facts" that come down to "I don't like it"), and, well, you get the picture. Even after finally standardising on 9mm for sidearms (because everyone else already had done that a long, long time ago) there are still large swathes in the US military sticking to .45 ACP, basically on sentimental grounds. It's called "stopping power" but if you go look for hard, verifyable facts surrounding it, you'll find precious little in it, certainly compared to the volume of other stuff in the debates. <troll>So, why cling to 5.56 when you have alternatives with more stopping power but insist on worshiping the 1911 and .45 ACP, eh? We have learned a thing or two in the past century, even if you haven't.</troll>
I don't really care much except that it is indeed stiffling innovation something fierce. And, well, perhaps not even there. We can already kill each other dead so much that if we'd put our minds to it there wouldn't even be a planet left. As you were, then.