I build two AR15's and both wasnt cycling the next shot. One of them I readjusted and it took off just like it should...I did the same for the other, but it still isnt cycling. It has a Spike upper, BCG, barrel, and lower (all spike). I am going to run through the build again and see if it helps. My focus is now on the gas tube allignment and the ADJUSTABLE gas block (the other is a fixed gas block)...we will see. I have a 90% finished AR-10 308 that I am checking thoroughly before having same issue.