Could damage your shoulder but it won't affect the gun.
One of my wife's brother's in law has a father, an old Dutch immigrant farmer who survived the Nazis, immigrated to Canada, worked hard on his dairy farm all his life, and is now very comfortably retired, surrounded by grandkids, and doing chipmunk/groundhog patrol on his one-acre vegetable garden with an old 12-ga SXS.
He's also the biggest, scariest, 80-year-old you ever saw. In terms of sheer wrinkly leathery old-dude badassery he makes Clint Eastwood look like Lauren Hutton. The guy is inspirational, and when I get old and crotchedy I want to be just like him.
Anyhow, his SXS was having trigger issues a couple of years ago, so he gave it to a buddy who had delusions of gunsmithing skills to have a look at. I don't know the details of what the buddy did to the gun, but after he got it back he went out to defend his veggies from the rodents. Apparently he was holding the gun with the butt braced against his bicep, and took a snap shot at a chipmunk.
Both barrels fired, and the recoil severed his bicep. The upper half retreated most of the way to his shoulder and swelled up. His entire right arm swelled up and turned black, and it took three days before his wife could convince him to got see the doctor about it (the guy goes so far beyond tough he can't see tough from where he is).
He's fine now, happily, but I saw him a month or so after the accident, when I was shooting some clays with the wife's brother-in-law; he was still having mobility issues with that arm, and still had a wierdass bulge on his arm up near the shoulder. He didn't shoot with us (his wife probably would have murdered him), but he was pretty interested in my 870 for some reason

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So in conclusion, make sure you have proper cheek and shoulder weld, and do put the results up on YouTube

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