I've shot several of the real-military M1 Carbines, and never knew of or heard of any problems for reliability. I prefer the 15-round mags, just for less awkwardness when carrying.
I dunno. They work, they're fun and accurate enough for plinking and casual bunny-hunting. Good little social gun, as well, particularly with soft points.
You're from BATFE? Come right in! I use all your fine products!