I bought a Green Mountain Barrel for my Ruger 77/17 to convert it to a 22 Mag and WOW!!! I have literally shot 1/2 inch 10 shot groups with it at 100 yards using Hornady 30 grain V-Max ammo. Somedays it won't shoot quite that well but when I get 10 shot groups over an inch it's really uncommon.
I like their barrels so much I'm saving up to replace the original 17 HMR barrel with one from Green Mountain. Let us know how you like it if you buy one.
I bought one of the Green Mountains barrels for my 10/22... It was their heavy barrel with the 1-9 twist too fire the Agiula 60gr sniper subsonic .22 long; it shoots fantastic, printing some very respectable 100 yard group. If I'm not mistaken, Agiula contracted Green Mountain to make the test barrels to develop the SSS round.
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I too have one and it immediately improved groups with cheap Federal ammo. Inexpensive, easy to install, good accuracy..........go for it, you won't be disappointed