A gun chambered to shoot Short, Long, and Long Rifle has a very specific chamber with a very specifc tapered rifling arrangement. If not the bullet can end up being canted when it hits the rifling farther down and the accuracy goes to pot really bad or worse. Most multi caliber rimfires are either bolt guns or semis that have actions that resemble shotguns that fire 2.75, 3, and 3.5 inch shells. The unusual chamber I mentioned is designed to get the shorter ammo's slug correctly lined up with the bore when it hits the tight part of the rifling. In a normal single caliber rimfire the lands start right ahead of the bullets correct OAL. In a multi when you put a LR round in it already is into the lands when chambered, just enough to line it up. The lands start just in front of the Short round's OAL. Most multi caliber semis I know of are tube magazine guns, oh gee, just like shotguns, I wonder why. Because of the difference in power they may have the alternate gas port arrangement of shotguns or not. For a semi to work is has to have springs light enough for the Short round to cycle plus a way to bleed off the power of the higher velocity rounds so that they don't slam the bolt into some kind of recoil pad.
Anyway I think if S&W ever found out you put Shorts through the AR15-22 they would likely void your warranty.
You might want to clean that gun as soon as possible as you might have lead pieces on the edges of the rifling that might cause issues with the LR rounds.
