American Rifleman did some testing on all the black rifle .22s in their Dec 2010 issue.

15-22 came in about mid pack among the bunch with overall 1.71'' average groupings from sandbags at 50 yards. (ammo used was CCI Tactical, CCI Select, RWS)

The best average groups were from the Ruger SR22 using CCI Tatical. Best group was .60'', largest was 1.03'', with an average of .85''. In comparison, 15-22 best group with CCI tactical was 1.08'', largest 2.10'' with an average of 1.75''. --- YMMV