Good points on proper gassing. I almost put a disclaimer in my original post concerning can and barrel choice. On my three 5.56 guns gassing is spot on (Centurion, G and Colt barrels) I loathe adjustable gas blocks for reasons. Using an OCL Polonium the gas to the face is not horrible but it exists. I have a K can on the way, which is supposed to be less gassy on the shorter barrels but time will tell. The gassy mo fo's are my two X39 builds. Port size on those is rather large at .090 and carbine length but they run and eject 100% Those two are running a Razor 7.62.