With a stout load such as this, be sure you have a good grip on the gun. Pull the buttstock back well into your shoulder, don't treat it like a delicate magic wand. A #2 AyA is generally considered a "field" gun, not necessarily designed for the heavy loads you are using, not to mean it wouldn't digest them safely. Try a 3 dram 1 1/8 oz or lighter load and get a good hold on the gun, see if that stops the problem.