Just out of curiousity, is there a way to tell the difference between a SP-1 upper and an M-16A1 upper if both have triangular HGs? Small front pivot hole, no forward assist or shell deflector, A1-style bircage FS.
Sure it's simple. The M16A1 had a Forward assist . All of them to my knowledge. The Sp1 did not have a forward assist as far as I know. I could be wrong about that.All Ive ever seen didn't. Colt had some funny manufactoring at times. Mixing parts that was left over to be so many rifles . I have a 1985 Colt HBAR A2 with a flat side lower. I bought it NIB.. Cheers WarDawg
I had a late model SP1 carbine. It seemed to be a way of getting rid of old production parts. The A2's were out. But to get the CAR It came with. 1:9 twist, A2 grip, round guards, round button forward assist. Shell defector, A1 upper with A1 rear flip sight. A2 Front sight
The early Colt M16s did not have a forward assist nor did the Air Force M16s from the early to mid 60s. The Air Force did not want a forward assist even after the Army added it. The Air Force was the first buyer of M16s not the Army. To answer your question yes on 16A1 uppers no on M16 uppers. The bolt and bolt carrage is also the some in a SP1.