2 1/2 oz? That's brutal. Tha tis like what the market gunners used to load into their 8 guage cannons. Enough to bring a big man to tears and choice words and maybe put him on his a$$. At 438 grains to the ounce that comes to 1095 grains or double loading 2 X 500+ grain conicals. The same volume of lead as powder was what I was told when I shot skeet with a friend's 2 barrel 12 ga front stuffer. A standard 12 ga shotshell load is 1 1/4 oz. I wouldn't push it past 1 1/2oz. Anticipating a heavy recoil can cause flinching = missed shots. Just my $0.02 worth.