Jack. you can use somewhat larger shot size to compensate for the lower velocity but it seems to me that other factors come into play. After all, these slower loads did very well in the past. There are many good articles about this subject in the Parker pages as well as the Double Journal. A great deal of research has recently established an interesting paradox which suggests that velocity has been over-sold as the answer to hunter's needs.
David

Jack: The English for many years ,[centuries even] have built and shot guns chambered 2 1/2" with an ounce of shot as their standard game load. The English size 7 shot is close to our size 6. It has only been of modern times, post WWI I would surmise, that they went to 2 3/4" chambers as standard. Even then you could order a 2 1/2" gun. I hate to think how many driven pheasant and partridge have been killed with a 2 1/2" 12 gage. I ordered #6 copper, and #7 lead loads from RST for my damascus gun and had no trouble killing a 21 lb. wild turkey with 1 oz. of copper 6's at 30 yards. The chokes are .022 and.034 and there is a swarm of pellets of both shot sizes at 30 yards.He was shot with the .022 barrel. I plan to shoot roosters with the #7 shot this fall. Maybe your Canadian birds are tougher than Kansas birds. The secret is pattern, pattern, pattern ! Have a nice day! Lee.

Pattern, Pattern, Pattern, Yes! For birds its Location, Location, Location, or should I say: Kansas, Kansas, Kansas!! David