carried M-16 A1 in Army 1983 -1986 have a couple of M-4 ,but just not the same as carrying my old A1 ,looking for something like what i carried 35 years ago ,which is better ,reliablility wise ? ,not worried if some small things differant ,but what about Fultons screwed front site? how differant is that and what problems would there be than from the original spring and pin?