First let me say that I have very little slug shooting expirence . My dad shot enough to be able to relate the this from a time when a rifled 12ga was twice as exotic as a screw in choke and those were about 1 for 10 with polychokes . With that said , rifled slugs or brenke type slugs will shoot fine even in tighter chokes . More open chokes like your imp cyl should make 3 inch groups with a fair amount of consistancy. My Dad shot 4inch 100 yard groups with a 50s vintage 30 inch bbl'd full choked Winchester mod 12 .