Tim,

I use a bronze brush on my re-barreld 40X.

22lr gunsmith who rechambered my 40X and the owner of Killough Sports both suggested using a bronze brush about every 300rds to get the carbon out of the throat. Both these guys have been shooting 22lr Benchrest many years, chasing itty bitty groups. I can definetly see a difference on target after a thorough cleaning. HAve about 10K rds on my barrel, shoots great.

Bronze brushes are the Devil, internet blather!!!