There's a thread discussing this very topic (15-22 accuracy) over on the Smith & Wesson 15-22 forums. If you find an ammunition that the rifle likes it can be pretty accurate for not being a target rifle.
15-22 Accuracy (For the nonbelievers)
they are a extreamly fun rifle. ive had one for 6ish months and have about 4000 rounds threw it. im actually getting rid of it because its to much fun and i end up shooting faster than i want to. a 25 rd mag doesn't last long at all. to me if the fun overrides my brain the training purpose is gone.
but i can take 4 shots and put them on steel @ 300 yards before the first one hits. thats a blast. i had a 1-4 vortex pst on it with a kill light 250, a bipod, ergo grip, huntertown arms suppressor