Don't forget the barrell.
I found your article in PS 634 (Sep 05) on headspacing and timing the M2 machine gun helpful. I hope Army gunners pay attention to it. But through my experience as a warrant officer and now an armament repair technician, there was one check I thought should have been included: the barrel.
When we check M2s, we often find the locking grooves that are machined around the barrel just ahead of the threads are worn. If they're too worn, the barrel locking spring can't hold the barrel in place, which means loose headspace. No M2 should be fired in that condition.
If you have doubts about the condition of the barrel, try to turn it with the bolt in the forward position. If it turns at all, either the barrel or the barrel locking spring is shot. You should always make sure the barrel doesn't turn when you headspace your M2.
To prevent barrel wear, gunners need to remember to pull the charging handle back to the 3/8--in hole in the receiver before screwing in the barrel. If you repeatedly force the barrel on without doing that, its locking grooves eventually will wear off.
Editor's note: Good point, Chief. Thanks for alerting gunners to a dangerous problem.
CW3 William Oxx (Ret)
Aberdeen Proving Groud, MD