The one thing that everybody seems to neglect is to check to see if both locking lugs are touching. If the bolt number doesn't match the receiver, you must always check. Because the Lee bolt locks at the rear, any unequal bearing of the locking lugs strains the bolt. In extreme case, the bolthead can actually break off. This usually happens if only the left lug is touching, as the right side of the bolt is largely unsupported. Lee bolts were all individually fitted at the factory, so keep this in mind. It's fairly easy to stone down one lug to make them both touch. I knew one guy who switched bolts, and backed his bolthead out one turn to take up the slack! Thank God the .303 is so mild. A hot load might have destroyed the rifle.