so far they been snapping under the full recoil of 5.7fn at about the 5th shot.
personally i think their trying to follow the prints of the USGI lower too closely.
if i was going to print a lower the entire thing would be wider than a standard lower and reinforced heavy at every known stress point.
it would be generally wider and thicker than its forged counterpart everywhere. it wouldn't be pretty--but it would be far stronger--
sort of like the cav arms one--
hell if it is breaking on 5.7fn what is gonna happen when some clown tries .50BW or .458 socom???-
i ain't saying a decent plastic lower can't be done--cav has done it.
just saying a reliable plastic lower ain't gonna look like a forging.
one of the problems is everybody wants the polymer printable lower to look like a forging--that is a no-no for plastic.