Just built an ar, mmc lower, brass forged aluminum upper, not sure of the manufacturer of the bolt, 14.5 in barrel, bc1.5 comp, h3 buffer, gun fires fine, but will either jam or won't pick up the next round after ejecting, thought it was a mag issue but ran multiple different styles and still won't function properly...thinking gas tube issue
This ^^^^^ Its way to heavy for a 14.5" IMHO unless it over gassed , I run a 3.8 oz buffer on a 14.5" PSA , I had a 4.2 and a 4.0 oz in it and it ran fine but it wouldnt keep the bolt open after the last round . Thats where I would start, in all honesty take a carbine 3.0 oz buffer out of another gun and try it first and see if it runs , Bet ya it runs perfect
I was all excited because I knew the answer. Feel like the kid in class who knows the answer so i raise my hand, and someone beat me to it. That buffer is way to heavy. I only run a H2 in my 7.5" barrel.lighten it up and see what happens.
Heavy buffer is a possibility. Could also be a gas issue. If the gas key on the bolt carrier does not appear to have gas escaping from under the gas key you could make sure the gas block is in the right position on the barrel. If you used a bolt on gas block it is fairly easy to push it took far to the rear and partly block the gas port. There should be a slight gap between the shoulder on the barrel and the rear if the gas block.