RR. there must be a lot better info available today because no one shoots or recommends that tight of constriction for turkey loads. the chokes like that is card shooter chokes now a days. and I suspect that the reason it works in that gun is as you stated. it is a sleeve. so you get a very even uniform forcing cone right into the choke so it gives the shot colum way more than enough time to transition and allows for way less deformation in lead loads.