Inspect the gas rings on the bolt carrier.. make sure they are well staggered and there gap is not lined up.. Buffer spring check. make sure gas key is clear and also check the gas tube make sure it's clear and installed right in the gas block.. Clean all grease out of the gun and for the first 100 to 200 rounds run her wet with Rem oil with Teflon..Oh and IMO don't use steel case ammo! George