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					Originally Posted by  Arthur Shaffer
					 
				 
				If there is a friction fit in picture #1, I am going to guess a chamber measuring tool. Insert the inner piece into the base until barely held, insert into chamber, close gun and reopen, then measure OAL. Looks like the inner piece is non-tapered and would indicate the length of a fired case. 
			
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 Sorry. I took the opening description to mean that the head part would fit a 12 ga chamber.
Sooo...
What is the the diameter of the rim and head section?  My same guess would cover a 10 ga or 8 ga chamber length gauge.