the last time i looked at the complete gun, it contained several proprietary parts that are not compatible with aftermarket replacements. which is not the case with the stripped upper/lower they sell with the same carbon 15 name
if you buy the stripped upper/lower, like I did, and make your own rifle with otherwise quality components, it can be pretty reliable. however, it may not last very long. i don't consider the complete guns reliable at all. and i think the pistols are just useless for all sorts of reasons
here's mine
they are very light, but the uppers are also pretty flexible. i can squeeze them with my fingers.
also, after 1500 rnds or so in 3gun matches (plus dryfire practice at home), the upper receiver latch that holds the charging handle wore smooth so the CH would move back when fired. bushmaster of course offered to replace the upper, but since i'd painted it, i didn't bother.
note that i'm also using a JP aluminum bolt carrier, instead of the normal steel BCG. i imagine this is a bit more gentle on the carbon fiber upper. and i have the gas port / ar-restor pneumatic buffer tuned so that the bolt doesn't hold open on the last round, which probably reduces some wear in the lower too. and i'm also using the jp trigger, which is screwed into the sides (kinda like KNS pins) so the lack of rotation, and the screws holding it together instead of just free floating pins probably helps reduce wear too
it is light though