If this is for fun shooting it is IMO a big big waste of money buying a dedicated upper.
A .22 conversion can be had for $140 and from what I have seen using my S&W M&P OR and CMMG conversion I would have no problems taking out small game at .22 LR ranges.
Target shooting I get 1-1.5 inch groups at 50 yards and 2-2.5 at 100.
Save your money for ammo and a few extra mags.
NRA Life Member, SAF Member