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Polishing a Rifle Chamber
by Roy Seifert

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Disclaimer:  This article is for entertainment only and is not to be used in lieu of a qualified gunsmith.  Please defer all firearms work to a qualified gunsmith.  Any loads mentioned in this article are my loads for my guns and have been carefully worked up using established guidelines and special tools.  The author assumes no responsibility or liability for use of these loads, or use or misuse of this article.  Please note that I am not a professional gunsmith, just a shooting enthusiast and hobbyist, as well as a tinkerer.  This article explains work that I performed to my guns without the assistance of a qualified gunsmith.  Some procedures described in this article require special tools and cannot/should not be performed without them.

Warning:  Disassembling and tinkering with your firearm may void the warranty.  I claim no responsibility for use or misuse of this article.  Again, this article is for entertainment purposes only!

Tools and firearms are the trademark/service mark or registered trademark of their respective manufacturers.

I recently replaced the barrel on my sonís M1 Garand using a used barrel.  That barrel came off of a Springfield receiver after having gone through an arsenal rebuild.  I never had any problems with that barrel when it was attached to the Springfield receiver.  However, after swapping that barrel to my sonís Garand, fired cartridge cases would stick in the chamber and could not be extracted.  In fact, the extractor was shearing off the rim of the case.  We could only remove the stuck case by driving a rod through the barrel.  This was caused by the thread-locker I used to install the barrel (refer to my article Rebarreling Two M1 Garands), which ran into the chamber and hardened causing a rough spot.  Time to polish out that rough spot.

There are a number of methods for polishing a rifle chamber, and all work very well.  The goal here is to just polish, not change any of the chamber dimensions.  I wanted to remove any burrs or imperfections; in my case dried thread-locker.  One method is to drill out the flash hole from a spent cartridge case so a cleaning rod attachment can fit through the hole and be used as a nut to hold the cartridge case on the end of the cleaning rod.  Then cut a slot lengthwise in the cartridge case, insert a strip of 600-800 grit wet/dry paper into the slot and wrap it around the case so it does not overlap itself, coat it with gun oil, then pull it into the chamber.  Rotate the case with the paper to polish the chamber.  This can be done by hand or with a drill turning slowly.  A little goes a long way here.

 

Many years ago I purchased a Flex-Hone from Brownells.  I have used this to polish the .45 LC chambers in my single-action revolvers (refer to my article Polishing Revolver Cylinder Chambers).  This is a better tool for polishing chambers and consists of small balls of polishing grit on the ends of a spiral wire brush.  The Flex-Hone comes in two different grits, medium and fine.  The medium-grit hone is used to polish-out the tooling marks, and the fine-grit hone is used to final-polish the chamber.  Brownells states that you should only use Flex-Hone Oil as the cutting/lubricating agent, and that you should not spin the hone any faster than 750 RPM.  This is well within the slow speed of my cordless drill.

A word of caution here; I do not want to polish the chambers mirror or bearing smooth.  When the cartridge case expands, it needs something to grip against; otherwise I could get excessive pressure, so I decided to use only the fine hone.

 

The Flex-Hone for revolver chambers comes with a shank that is only 1 1/4-inches long.  Brownells also sells a Flex-Hone for rifle chambers with a 14-inch shank, but I didnít want to spend the money.  My rifle cleaning rod takes an 8-32 attachment so I thought if I cut 8-32 threads on the end of the shank it would fit my cleaning rod which I could pull through the bore.  Using an 8-32 die I cut threads on the first 1/4-inch of the shank.  After cutting the threads the hone fit perfectly onto my cleaning rod.

 

I disassembled the M1 Garand and removed the action from the stock.  I also removed the operating rod spring and follower rod, operating rod, follower arm pin, operating rod catch, bullet guide, follower arm, follower and slide assembly, and the bolt from the receiver.  I mounted the receiver in a padded vise so I wouldnít scratch the finish.  I used a bore guide and pushed two sections of a cleaning rod without the handle through the bore until the accessory end appeared in the receiver.  I screwed the hone onto the end of the cleaning rod and attached the other end to my cordless drill.  I liberally coated the hone with Flex-Hone oil, pulled the hone into the chamber, then ran the drill at a slow speed for about 2 minutes.  As the hone turned I pushed it in and out of the chamber. 

When the 2-minutes were up I unscrewed the hone from the rod and removed the rod from the bore.  I cleaned the chamber and bore with brake parts cleaner, then thoroughly dried and lightly lubricated the chamber and bore with gun oil.  I examined the chamber with a good bore light and couldnít find any burrs or blemishes, but I could see the cross-hatch pattern left by the hone.

This time cartridge cases did not stick and ejected the way they should.  This method for polishing a rifle chamber helps to ease case extraction without damaging the chamber.

 

 
   © Copyright 2011 Roy Seifert.