I put some rounds through my newly built SPR today and afterwards took it back in to clean it. After taking the rifle down and removing the BCG to clean I noticed the gas tube has a slight rattle. I'm using a rifle length gas system so I didn't know if this was normal with the longer gas tube (first rifle length system I've had). The gas tube was solid at the gas block an didn't appear to have any gas blow by at the block. The rifle cycles perfect although sometimes it wouldn't lock the bolt back a couple times when shooting some Wolf ammo. Any thoughts?....