Hi I'm new in the pistol ar configuration but i get a ST 14.5'' .223/5.56 pistol my issue is the cycle on the bolt is short al least every 7 or 8 rounds no loading or double feeding the ammo i would like to know is maybe the buffer is to heavy (ST 2 buffer) or maybe losing gas somewhere in the cycling?

Pictures of lower and upper?

There's a few possibilities based on your description. If it is a brand new weapon from us, the usual culprit is not cleaning it before taking it out for the first time. Our preservative grease that the BCG is coated with can be pretty thick after test firing. If it is thick, then it can inhibit how smoothly the bolt rotates in the carrier.