Originally Posted by pomofo
What is the interior dimension of your 10-gauge chamber just above the rim? What is the diameter just above the rim of the existing fired cases that will fit? What is the diameter just above the rim of the fired cases that won't chamber? That would determine how many thousandths you would need to resize.

SAAMI spec is here, page 19: https://saami.org/wp-content/upload...shell-2015-R2019-Approved-2019-04-23.pdf

Diameter of 10-gauge 3.5" just above the rim is 0.854 - 0.009, meaning that your 0.846 is right about at the very smallest diameter possible. Not knowing the dimensions you're working with, If I were you I would try opening up the 0.846" hole to about 0.850" or 0.852" for the first inch or so and see if that takes care of the problem.

The smallest number I got was .850

I think a combination of an arbor press and perhaps carefully reducing the amount of brass near the hull rim will be my best bet with the equipment I have available. The thickness of a RMC 10 g at the mouth is .030, the diameter at the mouth is .840 widening to .853 right above the rim. The good news is that the RMC hulls will probably never wear out, the bad news is if they are too big for a specific gun, they are a serious pain to re-size.

I have become addicted to English hammered shotguns to the detriment of my wallet.