Fast Twist Subsonic Barrel Fits the Ruger 10/22 rifle. This barrel features a 1:9 rifling twist to stabilize slower, subsonic .22 ammo such as: Aguila 60gr SSS Super Sniper, CCI Green Tag, Wolf Match Extra, RWS Target, etc. Subsonic ammo shoots quieter because the velocity doesn't break the sound barrier. The "slow and heavy" bullet approach puts a TON of whack on small game, too. Just ask any old timer about how his old 22 short seemed to kill squirrels better than 22 LR ammo. Subsonics do the same thing only they fit properly in a 22 LR chamber and give much better accuracy because of it. Subsonics are a neat concept... This is a beautiful blue fluted Ruger 10/22 barrel, 20 inches long and .920 diameter heavy contour.