Lones Wigger, who's probably won more smallbore matches than anyone in the USA, cleans after every 50 to 100 shots.
Neal Johnson, who's shop in Colorado Springs does a lot of work on Olympic team members rifles, says to rebarrel .22's when the black erosion ring has worked its way up and around from 6-o'clock to 9 and 3 at the origin of the riflling. That happens today with the ammo available that shoots the most accurate at around 30 to 35 thousand rounds.
Rimfire barrels used to last twice that long in top level competition. But that all changed in the 1980's after the ammo company folks changed the primer mixture for safety after a blast in Eley's Great Britian plant killed a couple employees. The best rimfire ammo made since has never equalled what the stuff before had for accuracy. No wonder that most of the smallbore records set before then still stand.
Last edited by Bart B.; September 9, 2012 at 09:20 AM.