I have a M&P Sport II that I've been replacing the parts on. I replaced the barrel with a BA hansen mid length barrel. At the same time I also replaced the BCG with a NBS nitride bcg from AR15 discounts. When I took the rifle out to the range to test fire wouldn't reliable cycle. I switched out the bcg with a toolcraft from another rifle and it cycled fine perfectly. I've also tested with the original bcg from the M&P and that cycles fine. I returned the NBS bcg for a replacement one and while the rifle will now reliably cycle it still won't lock back on the last round. Should I chock this up to NBS just being garbage or is this possibly a problem with my gas system?