As an addendum, I did experience a period after about 250-350 rounds had gone downrange where the groups weren't so hot. A CAREFUL cleaning with some JB's Bore Paste and Hoppes Benchrest 9 set things right again.
Let's face it. Most of you guys don't clean your barrels often enough, or correctly, or, for that matter, ENOUGH.
Hoppes solvents don't cut copper very well. Even their "benchrest" stuff. When copper gets built up, you'll get a decrease in accuracy, and an increase in pitting, etc...
Clean every 15-20 rounds. That gets the copper before it has a chance to build into something ugly. You also want to get the carbon out. Even with VERY careful cleaning, you'll get an accuracy-degrading carbon ring at the throat, and you'll need to brush with Iosso occasionally to get that out. Some folks use JB bore paste - works fine.
Use a one-piece rod - Proshot, Dewey, whatever. Brass/bronze-core brushes, brass/bronze jags, etc. Use a flippin' BORE GUIDE to keep things centered. Spend the extra effort and get one from Mike Lucas or one of Sinclair's. It'll custom fit your action/chambering, and won't cost more than a few bucks more than one of the generic ones (which don't work all that well. I prefer Lucas myself.
Get the bore CLEAN. That means use a good copper solvent. I like Butch's Bore Shine, but anything that uses plentiful ammonia should work okay. When you think it's clean, run a patch of Sweet's in, then wait a coupla minutes, and run a dry patch. If any blue/green shows up, it ain't clean.
I'll run three SOAKED (keep 'em in a jar on the bench) patches with BBS, then one stroke/shot with a brush (soaking it), then let it sit for 10-15 minutes. Then it's three soaked patches to flush out the crud, then three dry patches, then a patch with a couple of drops of lock-eze on it.
My gunsmith says to load 20 pieces of prepped .220 Russian (for a 6PPC). Jam the bullet hard. Fire one, clean, repeat for five rounds. Then fire five three-shot groups, cleaning between them. You've now fireformed 20 pieces of brass, and accomplished a barrel breakin procedure.
