Sudden: The trouble with "old" steel is that it couldn't penetrate very well and often crippled birds rather than kill them. We're told that the "new" types of steel ammo have eliminated that problem, mostly by significantly boosting velocity and, as a byproduct, pressures.
I agree with Ted that, short-term, you're unlikely to do an open-choked 311 much damage shooting these loads, but if I was going to try waterfowling with a 20-gauge (which in my neighborhood is a handicap employed by only the very best of shots, and a mistake made by the least experienced of hunters), I'd be kinder to my gun, and give myself a bit more of a chance, by shooting bismuth or another of the premium options.
Voice of experience here ... buy 20 rounds of the pricey stuff and go on a hunt. You'll use half of them, get the 20-ga. out of your system, and then switch back to a 12-ga. without having spent more than a few extra bucks. Shoot straight and happy hunting. TT
