The main problem seems to be using this stuff in rifles with fluted chambers. In essence the case is somewhat unsupported where the flutes are and it causes it to blowout (not as ductile as brass). It should be noted that some guns with fluted chambers such as the HK G3 are problematic with regular ammo (don’t like Winchester .308, for instance. These are not gas operated, but delayed blowback in operation. That explains the PTR91 (CETME, G3 clone)blowup, but not the FN FAL.
I’d like to mic a fired brass case from the FN FAL.