My Colt HBAR A-2 recently started having an issue. After the last round is fired, the bolt stays open, however, when I place the gun in the rack, the bolt will close. It seems with a little "thump" on the butt stock, the bolt will close. A buddy at the range told me i had too much oil in the gun, and he's probably right. I was told to run the gun "wet" so i have been applying oil pretty liberally. Could too much oil cause this problem, or do i have another issue?