Question About Rifle Bolt Faces

[ready05]

Hello All,
I have a question in regards to bolt action bolt faces. I have seen on bolt faces where there are small pits in the bolt face metal about where the outside diameter of the primer is. The pits form a round ring, about the size of the primer. Are these pits in the metal from heavy loads or appear over time from many firings? Curious to how and why they develop. Loose primer pockets? Thanks for your knowledgeable response.

 

[Eddie Harren]

Hot gas leaking out around primers is the culprit. Hard to contain upwards of 50,000 PSI with a seal that is formed by very slight hand pressure.

 

[ready05]

Thanks DocEd,
That is what I thought. If one is looking at buying a rifle that displays a good ring of pits, better to spend ones money elsewhere? I would think it would take many firings to develop a good ring of pits. What do you think?
Thanks again.

 

[KevinThomas]

Ready05,

The pits you've described here are most likely the result of primer pocket leakage, burning the small pit in the face of the bolt. This can be caused by heavy loads that are leaking pressure through the primer pocket, or by defective primer cups which are leaking gas directly. either way, the result is a pitted bolt face. Not a good situation, and can (will) eventually cost you a new bolt.

 

[KevinThomas]

Whoops! Started answering this one before DocEd, and got sidetracked with a phone call. Agree with his post completely, not a good thing.

 

[fdshuster]

Also caused by blown/ruptured primers. They will fail at the top, rounded edge & when they do, the burn holes in the face of the bolt will result. Had a Springfield that was damage free 'til I used a batch of Remington Large Rifle primers that had several failures. Now that bolt face has 3 or 4 "holes". Has nothing to do with how many times the rifle has been fired, could happen with the first firing of a new rifle. When/if the rifle is ever re-barreled the gunsmith can easily face-off the bolt & it will be as new.

 

[Robert]

Whoops! Started answering this one before DocEd, and got sidetracked with a phone call. Agree with his post completely, not a good thing.

The causes are well know, but the effect can depend on the alloy and treatment of the bolt steel. I wonder if a hard refractory plating/coating of the recess face would not somewhat reduce/eliminate the problem?
R.G.C

 

[tenring]

Many years ago, I bought a hunting rifle in .243 with the same condition. Gunsmith looked at it and said the pitting was about .005" deep, and could not be corrected unless the barrel is moved back. But it was safe to shoot.

 

[CaptainMal]

One year Remington replaced a bolt for me on my 40X. Bad lot of Remington primers with breaks in the cup material.

Remington was great, the gun was/is great, there were no issues with the loads, the bolt-face just got cut badly by plasma-like gasses leaking around the primer cup.

It can and does happen quite often.