Regards to Mossbergs, fit, and recoil....8 or 9 years back when I was a newb to this board, I'd been shotgunning for over 30 years, mostly waterfowl and doves. I knew some guns were sweet, some beat me up, but I'd never really considered FIT. I posed the question on this very board. I'd go duck hunting shooting heavy steel shot loads and come back looking like I'd done 3 rounds with big George Foreman, face would actually be cut and I'd be bleeding like a stuck hog from the upper jaw line of my cheek. Even light dove loads would bruise me up a bit seeing as a 3 or 4 day hunt, I'll shoot a lot more rounds dove hunting than duck hunting.
I was told I didn't likely have enough drop on the stock. They were right. I had to crawl the stock a bit to see down the rib and that was the problem. I cut pop bottle plastic as instructed and lowered the stock with the shims I'd made and got the thing to come to me nicely without crawling the stock. NOW, as oneounce explains, I can close my eyes and bring the gun up and open my eyes and I'm looking right down the rib without having to lower my head to the stock a bit. THAT fixed the battering problem, but more than that, I got faster with the gun on target and my shots per bird dropped a LOT, I got more efficient with the gun.
Now, I often shoot one for 2 shots on doves, tough little beggars to hit, where I used to do good to hit 1 for 3 or 3.5. It's all because the gun now fits and I shoot where I look with it.
Some guns will fit right out of the box. I seem to have a Winchester/Browning build. Mossbergs ALWAYS need more drop. But, no problem now that I know what to do to adjust the stock. Mossberg even offers shims for this, but pop bottle plastic and a little time is cheaper for a retired person.
I got lots of time.
Now, if your shoulder is still painful after 15 or 20 rounds, the Limbsavers help. I have one on my Mossberg 535 and an old SxS that I've had for years. If you think buckshot is tough on you, try a 3.5" 12 gauge steel T shot load from a light 535. That's why I got the Limbsaver.
But, work with fitting the gun to you, also. It really helps for the gun to fit right.