Allso keep the chamber clean! Clean it good and let it soak in the chamber to get out all the varnish out of the fluted areas. The flutes keep the brass floating on gas,s to keep it from sticking in the chamber. The same fluted system was used in the Hk G3 designs and MP-5. Even bolt Mosins can load up on Com-bloc varnish gunk and make it hard to extract. Brass case PPU from Aimsurplus new nc,boxer primed is what I shoot in my SVT40 with mint bore and gas system.