Many of the 12 ga. slugs marketed today are honkin' fast and high pressure. I recommend Breneke, and tamer ones at that for the tighter chokes, else a ring bulge behind the choke at muzzle could be a possibility, though a slight one. Buckshot is finicky and not so subject to constriction for safety reasons. Try it out for buckshot--the regulation for slugs will probably not be affected by choke very much. (lengthening forcing cones, YES) Your gun may be regulated for slugs NOW, from factory. One gentleman on the forum claims he gets 10" patterns at 40 yds. with his Sauer 3000...maybe you could research the choke configuration as well as constriction if that be so.
