For real accuracy, a long barreled .22 rimfire with std velocity ammo is the most difficult. The shooters technique, position, follow through, trigger control all must be letter perfect. The extremely slow bullet (1050 +/- fps) makes all the above critical. It might have virtually no recoil, but the rifle starts moving when the bullet start moving. It's up to the shooter to minimize all the above for real accuracy. Add to that, the lot to lot variations in .22 rf ammo, poor ballistic coefficient, sensitivity to crosswinds and variations in priming mix distribution.
I see smallbore benchrest shooters at my club with VERY expensive hand built rifles on rests that cost another huge sum, struggle to be able to shoot groups of 1/4" at 50 yds. While a CF rifle with similar equipment will easily shoot 1/4" groups at 100 + yards.
Roger