What did you have in mind? I think they would work fine on a ar15 for range use. I would not put them on a gun your life depended on. I am guessing the recoil of a large caliber rifle or a shotgun would damage them, but I suppose there is only one way to know for sure. If you want to try and your wreck them no big deal, get a heavier set.
I don't know that they are, but they don't seem to me to be real high quality. They are a piece on a .22 that most of us remove and discard. Smith and Wesson knows that. I don't think a lot of time and money went into them.
Like I originally stated, I don't know that for sure. If he wants to try them on another gun go ahead. We will not know unless someone gives it a try. If they break he can buy another set, no big deal.
A plus with the standard 15-22 rear sight is that it's adjustable for elevation, and without need for a tool. I prefer this to, say, a Magpul folding rear sight that's only adjustable for windage, and requires carrying a tool to adjust the height of their folding front sight post (I have Magpul folders on my 15-22). Does anyone make a folding rear sight that's elevation-adjustable without a tool?
I run a Matech on the rear of my M&P 15 OR and the stock 15-22 sight on my gas block. It's held up fine with around 2,000 rounds through it. Just added a little blue loctite.