whats the best way to smooth out a rough throat in a 22LR?

[chuckbuster243]

Hello guys,
I have a 22 bolt gun with a pretty rough throat on it. Its shoots well but leads up fast and accuracy degrades after 50 shots or so. I checked it with a borescope and the throat is pretty darn rough with a good bit of machine marks fairly visible. I was just wondering what would be a good method to just smooth the throat out to help the leading and extend the accuracy window. Thanks, Matt

 

[langenc]

I have some ideas but will be watching tosee what some w/ experience say. I have a gun that may need a little 'help'.

 

[Outrider27]

I know that "fire lapping" bullet kits are available (the only system I have any familiarity with uses 5 progressively finer grades of abrasive) to handloaders for just this purpose. I don't know if ammo or roll your own abbrasive kits are available for creating .22 RF barrel polishing rounds. Brownell's or Midway might be places to start a search. FinalFinish (one word) is the name of one such product kit, and I believe Brownwlls carries it, but again, I'm only aware of centerfire kits.

It is also possible to hand lap the bore using lead plugs (pulled .22RF projectiles are the best, I'm told) and a proper lapping cpmpound. Bill Calfee discusses .22RF barrel slugging and hand lapping in considerable detail in his book "The Art of Rimfire Accuracy".

 

[rayjay]

I use a split arbor and worn 400 or 600 paper depending on how bad the roughness and burrs are. Then I polish with Flitz impregnated patches on a regular jag.

The arbor is spun in a cordless drill while the bbl is in the lathe. Spin the drill one direction with the lathe the going the other. Then reverse both [ and the direction the paper is wound on the arbor. Only takes a few seconds in each direction. The clean from the muzzle and check with borescope. Repeat until the rifling is burr free and smooth. Then do the Flitz.

Don't run the arbor in farther than the leade.

 

[chuckbuster243]

update....

I polished the throat using flitz on a patch wrapped around a brush. I only did from the chamber up into the throat. So I shot the rifle a few over 100 rounds until the groups started opening up. Took it home and run a borescope in it.... Well the throat was clean where I polished it but the rest of the barrel is packed with lead! Crap I guess I need to keep polishing.... Thanks, Matt