Jack, I have not shot sporting since '01. So it was before that and I believe we were doing like everyone else in those days, using 1 1/8.
We never adjusted anything or even remotely tried to figure out the weight/volume, except what came through the shot bushing. We shot quite a few targets in the 35-40 yard range and felt we broke what we deserved.
Although with all the shooting we did, I would not try and attempt to convince anyone it performs the same as Magnum shot. We were both shooting in the high 80's low 90's in those days, so we should know if the shot was at fault.