Was doing some filming at the range the other day, had both the Colt LMG upper and a newly acquired Colt IAR upper out, each on on a full auto lower.
Colt LMG upper always runs 100%
Colt IAR upper will run on semi just fine, but gets hammer follow in full auto, max 2-3 rounds before a dead trigger (i.e. hammer follows).
The IAR upper was being run on a carbine length buffer tube with I believe (will have to confirm) an H3 buffer.
Swapped the Colt IAR upper to the lower we were running the COlt LMG upper on, rifle length buffer tube and hydraultic buffer. Exact same thing, dead trigger after max of 2-3 rounds on full auto, runs fine on semi.
Swapped the bolt carrier groups between the two uppers, tried on both lowers, still get a dead trigger after 2-3 rounds.
I know it is a timing issue of some sort, any suggestions beyond what I have already tried? this one has me a bit stumped, and being the upper is an original IAR upper, I don't really have options for a tunable gas system, etc.
We only have the two full auto lowers to try it on, but I can try some other bolt carrier groups, and I can always switch buffer weight on the carbine lower and go to a standard rifle buffer and spring on the rifle lower.
Sven
Manticore Arms