Twas me I'd get rid of the longish 20in barrel for one about 16in, to be legal! (18inches is more than plenty is a .22LR)
The .22LR maximizes performance around 14-16 inches depending on the particular loading. Anything more than that creates a drag on the bullet. Data is available on this. A 10inch bbl doesn't quite equal a 14-15-16in tube, altho it comes close to a 20incher!
The .22 Short maximizes performance at @11in, the .22WMR at around @19in, and the .17HMR around 21inches.
Also I'd get a barrel in HB or semi-HB contour, similar to a design offered by Clark or Clerke barrels that's heavier than standard Ruger tubes. The HB's are @.920 in diam. and the semi-HB is @.720" at the muzzle.
Also if you want a specialized long distance shooter, getting a custom barrel that screws into the receiver rather pinning it in, might help some too. But whatever you do, once your rifle is set up with the type of barrel you want, the trigger group tuned, on the stock you want with the scope and mounts you want (or whatever iron or peep sights you like), you need to try and compare several kinds of .22 fodder - whatever you can find and are willing to afford.
For 100yd plinking, but for accuracy ..... I'd splurge a little for specific ammo my gun liked as well.
Standard vel ammo should be around 1070fps, which is the same as subsonic ammo, and rounds like the CCI green Tag and Pistol Match, and many more expensive Lapua, RWS, or other brands too.
But often folks get lucky with the Federal (Walmart) promotional 550rd cartons. Can't remember the number of folks I've met who love that stuff!