From my own experience and contact with RimfireCentral, it seems the Ruger factory target barrel groups better than the stock barrel, but not quite with say, a Kidd, Volquartsen or Fedderson.
If you can find a very early 10/22, it should shoot good also. My first 10/22 was a first year model, #66XX, it would outshoot some very expensive rifles. I have been told that the earliest 10/22s had barrels supplied by an aftermarket maker..
Who knows? Green mountain isn't too far from Southport, CN !
Only kidding, Green Mountain, in Conway, NH ..wasn't started until 1976