Originally Posted by
shortround
Bolt gap on the HK's are checked with the hammer down on an empty chamber. Let the bolt carrier fly home after checking to make sure it's empty. Then pull the trigger while pointing the rifle in a safe direction. The gap between the carrier and the bolt head should be at least .010" and less than .018" (.25 to .45mm). If your normal is .005", your gap is too tight. Wrong bolt gap can lead to early unlocking and excessive recoil. If your rifle was firing without your bolt "locking", it would be very unpleasantly obvious.
The amount of marking on the case can vary with the cartridge make. If this is a factory rifle, I'd be very surprised at the bolt rollers being worn unless you have a great deal of rounds through it. My '91 from the late 80's has in excess of 8k rounds through it and still has a very acceptable bolt gap.