Does the 15-22 use a standard AR15 one? I want to change mine out, but not sure it will work.

They are not the same. I have a standard AR bolt release catch in mine and it needed modifying to make it work. I had to weld a higher tab at the top and grind out the lever so the upper would fit. Yes, it can be done but why, whats wrong with the stock one?

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15-22 bullpup, "X-terminator"

I wanted to put one with the large tab at the bottom to lock the bolt back easier. I have them on my AR's, but if it's not drop in I won't bother.

Thanks for the info.