Can not help on the 30/40  06 conversion, other than thinking the barrel should have been set back before reaming the chamber.

Does part you are looking for look like the one in attached photo? if so it maybe your barrel band was originally made for a 340 Savage rifle. I made an experimental conversion for another member's Krag. Instead of tapping for the savage 1/4-28 screw we did the 10-32 on the vice. If this is what you are needing I can make some more.

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