Try an Armalite Buffer Spring it has 34 coils and is stiffer than the DPMS buffer spring which has 30 or 31 coils. I have a problem with installation of part of a system. (I.E. JP light weight bcg ,spring and buffer.) It works great if you use all of their parts together. If they are used as individual parts problems happen. Also with a fired round, put a brass in the chamber , remove bcg. Plug the end on the barrel and get a can of air , insert the little red tube into the gas tube inside the upper recever ; Then blow the brass out with a quick burst of air. If it sticks ... check gas block alignment or rough chamber ! Hope this helps.