The BOSS Bismuth loads are made in the U.S. so will follow the SAAMI pressure limit of 12,000 psi for 20g
The 2 3/4" load is 7/8 oz. at 1350 fps

The recoil would be significantly greater than the recoil of the loads for which the gun (and esp. the stock wood) was designed. Personally, I wouldn't consider those loads unless the head of the stock was glas bedded or cyanoacrylate impregnated.