Can you overpolish a rifle chamber?

[Scott Harris]

I recently had to polish a newly chambered barrel that was putting a deep scratch in all my cases. After using a 800gr flex hone and JB past, the chamber is now very polished and I've heard that this may not a a good thing. For those that say this is a bad thing, what evidence do you have to support your position? Thanks.

 

[Preacher]

2 school thoughts about this, but I'm thinking that a highly polished chamber will increase back thrust, because the chamber walls don't have a tight grip on the case..
If your running sane loads I doubt it's a problem..
I polish chambers to 320 grit and leave it at that...

 

[BoydAllen]

Just make sure that your cases have all of the sizing lube removed, and that you thoroughly dry your chamber after cleaning, and you should be fine. A friend had thought that using a chamber swab was doing the job for drying his chambers, but he would get unusual pressure signs on the first couple of firings after cleaning. When he switched to something disposable for drying, the problem went away. I mount an old bore brush on my chamber rod, and loosely wrap it with a strip of paper towel, wound on a taper, overlapping both ends of the brush. I push it as far as it will go into the chamber, give it a couple of twists, and then reverse the paper and repeat.