New Barrel? Be Safe–Check Your Headspace!

A friend of ours recently took delivery of a new barrel which was chambered by a smith who had done the original build on the rifle, but who had not headspaced the barrel on the action itself this time. The smith headspaced based on his old records. Our friend happily screwed on his nice, new barrel and headed to the range. After the first few rounds, with known, safe loads, he was seeing deep craters on his primers, and then he even pierced a few primers with loads that should never have done that. Interestingly, the brass was not showing any of the other pressure signs. This was with bullets seated .015″ out of the rifling.

We were thinking maybe too much firing pin extrusion or maybe he got a hot lot of powder. Then I asked him to email me dimensions off his fired cases compared to new, Lapua brass. He emailed me that his shoulder moved 0.0105″ forward. I sent an email back saying, “hey, that must be a typo, you meant 0.0015″ right–so your shoulder moved one and a half thousandths correct?” The answer was “No, the shoulder moved over TEN thousandths forward”. Ahah. This explained some of the cratering problem in his brass. His cases were able to bounce forward enough in the chamber so that the primer material was smearing over the firing pin. And now he has brass that is “semi-improved”.

The point of the story is always check your headspace when you receive a “pre-fit” barrel, even from the smith who built the rifle. Purchase Go/No Go gauges for all your calibers. Headspace is not just an accuracy issue, it can be a safety issue. Pierced primers are bad news. The debris from the primer cup can blow into the firing pin hole or ejector recess causing a myriad of problems.