Mine too. One thing I learned from my WRA library is that both the WS-1 and WS-2 chokes were machined on a 17 ft. radius. I have 2 older M12's that have "uncommon" factory chokes- (1) a 1939 era M12 field grade 28 ga. 28" solid rib choked WS-2, and a 1949 era Pigeon Grade Trap gun 30" Ventilated rib (duckbilled) and it is marked Imp. Mod. instead of the more commonly found Full choke.
Best way to determine the choke(s) in your shotgun is to pattern test it with the actual loads you plan to shoot- IMO RWTF.
