The Firing Line Forums - View Single Post - Different ways to chamber a rifle barrel?

Gunplummer · June 5, 2013, 10:09 PM

You have misunderstood the idea. It does not matter if the case springs larger than it was in the die. You are measuring the case not the die. You give yourself enough on the neck dimension (SAMMI). The little bit the neck expands really won't show up. I made a bolt for a rifle with excess headspace once. The chamber was oversize. I got rid of the excess headspace, and a fired case hardly grew in length, but when re-sized the OAL grew about .015 . The case walls expanded outward. That is an extreme example of what an oversize chamber dimension will do. Using ammo that was manufactured on the low in chambers cut on the high will give you the same effect. If mixed ammo is all resized and fired in a chamber matched to it, the OAL increase when re-sized again is almost non-existent. With the new CNC grinders that tool shops use now, I don't see why the idea is not more popular.

June 5, 2013, 10:09 PM	#20
Gunplummer Senior Member Join Date: March 11, 2010 Location: South East Pa. Posts: 3,364	You have misunderstood the idea. It does not matter if the case springs larger than it was in the die. You are measuring the case not the die. You give yourself enough on the neck dimension (SAMMI). The little bit the neck expands really won't show up. I made a bolt for a rifle with excess headspace once. The chamber was oversize. I got rid of the excess headspace, and a fired case hardly grew in length, but when re-sized the OAL grew about .015 . The case walls expanded outward. That is an extreme example of what an oversize chamber dimension will do. Using ammo that was manufactured on the low in chambers cut on the high will give you the same effect. If mixed ammo is all resized and fired in a chamber matched to it, the OAL increase when re-sized again is almost non-existent. With the new CNC grinders that tool shops use now, I don't see why the idea is not more popular.