Call Smith and Wesson and buy a replacement gas block from them. Weather or not it will work with the outcome you hope for is unknown, it should be able to be done. Hence us pointing you to the 15-22 forum.
Ultimately the part you're looking for will end up on a 15-22 right? TDI Brad took it a step further and posted a link!
I don't have a 15-22, but I would bet it has a slimmer profile barrel. So finding a gas block that fits that barrel profile is going to be the challenge. You might find out that such a thing does not exist (just playing the devil's avocado), so you will have to find some type of spacer to fill in the extra space that the profile won't meet.
Someone has probably tried this or something very similar, but the knowledge base for the 15-22 is going to be 100x greater in the 15-22 forum. While a lot of add ons are the same between the rifle, most working specs are not, and guys looking for info on their mp15 probably are going to skip a post about a 15-22!
If I am coming off as rude, I'm sorry I am not trying to be. Just trying to enlighten you to go ahead and try this post out in the 15-22 forum.
