[Waldo Pepper]

I read somewhere last year someone did a test with some of the hyper velocity ammo and 18" was slightly more then enough barrel needed to burn the powder, but accuracy was a different story. Seems best accuracy was with 16" barrel and the drop in velocity that caused better bullet placement. IIRC they never found a better length then about 18 or 19" for any 22LR ammo and the super fast ammo was less accurate as a rule and they figured it was all about bullet design and velocity.