I have an interesting problem. I came across two gorgeous stocks and am in the process of refinishing them. One is an Athena Butt stock and one is an Orion buttstock. There is also a fore end that matches one of the buttstocks. My problem is that I do not know if the buttstocks are for a 12 gauge or a 20 gauge. The fore end is for a 20 gauge. Is there any way to tell if the butt stocks are 12 gauge or 20 gauge. I meased the opening at the end of the stock where it meets the receiver. On the orion stock it is 13/16" and the athena measured 29/32" I have a feeling that the Athena is a 12 gaughe due to the bulk of the stock but am looking to find out for sure. One other question as well, for the fore end, are the athena o/u and orion o/u fore ends interchangeable. If not, how would one tell them apart?