Best guess is that the mag catch assembly is not installed so the threads of it are flush to the button, or if they are, then the mag catch is out of spec and the mag is sitting too low in the lower receiver when locked in (if the other mags you are trying are USGI, and not some crap after market brand).


Really, make/brand of the rifle, and type/brand of other mags you are trying would be helpful to take this any farther.