Thanks to all for the replies, i was doing some searching and found buying a the upper is more expensive then just buying the base model from Smith and Wesson so i will probably be doing that as it's cheaper and again thanks for the info
I just recently bought a Sport 2 556 and was wondering could i replace the upper with a 22 lr when i want to do alot of shooting or would i be better off just buying a whole new one for that