I used 150gr. and 191gr. in my 2 3/4" 12 bore double. Yes- they kick a bit, even broke my stock through the wrist. I repaired it and it's still shooting, 15 years later by and for it's new owner on ducks over decoys and moose with balls while duck hunting - every year so far.

He is using high velocity smokeless loads for duck loads, straight out of the Lyman book, matching ball weight to shot load (1 1/8oz.) - low pressure using 4756 and 7625 powders - loaded as I've been suggesting for all these years. He is using a 14 bore ball, and the gas check off trap wads to hold it in the middle, cup-up, under the ball, then fibre wads (or cuttoff plastic wad) for taking up the excess space. He also uses one-piece cases like, WW but not necessarily WW make. I gave him several bags of old wads from herters and others along with the guns. He uses whatever fits and never has a problem. The powders and wads he's using probably are keeping his 'stats' to about 1,300 to 1,400fps. They sure kill moose. My brother shot a nice cow with a RB from his Brown Bess, 1728 model (.774" bore using a .735"(600gr.) ball, 100gr. 2f, 1,000fps, range 100 yards, pure lead ball. The ball smashed through sholder blade and then ribs on both sides, went straight (which slugs won't do generally on moose) through both lungs, making 4" diameter permanent holes and stopped against the hide on the off side. More velocity is just icing.

BTW - 150gr. is not bad on recoil at all and regulated, just as the heavier one, and with a bit of practise the 7 dram load isn't too bad either. First one took me by surprise and spun me around like a weather-cock - but didn't hurt --- much or for too long. I wouldn't call that insane, however I'd recommend a heavier gun than 7 1/2 pounds.