Thanks again, I talked to the gunsmith this afternoon. The bore diameter stamp is 15.9. That converts to .626 inches, a little closer. He is going to calibrate his gauge and read it agian.
Other stamps are CAM .70 and HE 1.200 . I was on a cell phone in a poor service area, I'll try to get more info later.

I usually use the choke chart on Hallowell's site. It shows 20g, .005-.011 IMP and .012-.019 MOD
terc

Last edited by terc; 08/06/13 01:37 PM.