Ruger shows that the 10/22 target models have a "proprietary" chamber.
"Proprietary, enhanced semi-auto chamber proven to increase accuracy and precision while not compromising reliable feeding and extraction"
I have one of Ruger's heavy stainless match barrels, but prefer the 24" fluted sporter barrels from Green Mountain that come with a Bentz chamber. I also have a couple of 10/22s that have been through the full CPC tune-up and they all shoot as well as I can shoot them.
I currently have 18 10/22s and the one that I shoot most often has been tuned by CPC. It has the 24" GM barrel and an American style stock with the high comb module installed. It shoot any good ammo into small groups. It even shoots the Winchester-Olin M-22 ammo better than most other plinking grade ammo.
