Same in Jasper National Park here.

The thing I do NOT like about the standard Foster slugs, is the hollow base limits weight 1 1/4oz. Feds are the heaviest(best of those), I think and promotes the base flattening out around the front end, disking, I guess you could call it.

The more solid Brenneke and Gualandi slugs seem much 'harder' in this regard.

I have some here that shoot well in my rifled Mossberg, that are labeled "Made in Canada", but it is obvious they used the Gualandi slug.

492gr. conical in shape with hard base attached. 1,610fps - going by the name: Challenger.