Hey I am building well trying to anyway my first AR. I have a gen 4 matched set 308 from SI Defence and they are a fine piece of work. I have 20 in megowen SS barrel being made in hbar profile with a rifle length gas port gonna run a heavy buffer and spring in a magpul PRS and an adjustable gas block I have some questions on all the pins to put everything together I don't know which ones work armalite or dpms and was wanting some info on what trigger,BCG(if one ever comes available ) I should use, and rail system thanks for all your help