by Dana Delesoy
GunsmithUSA Contributor
Continued from Part 1…
After every 10-20 strokes with the file I cleaned the file with a brass bristle brush, and measured the depth of the unsupported area with calipers. If the depth measures .029″, then .002″ unsupported area has been removed. Clean the chamber with a Q-tip and check for cartridge seating using the same method as for checking chamber smoothness.
IMPORTANT NOTE: Filing may produce a burr around the inside edge of the chamber. If it does, remove it with a deburring tool and polish with a tapered felt polishing bob. Refer to the photo “Chamfering the Chamber edge” below.
I recommend avoiding chamfering in the extractor cut area in the barrel, because an unsupported area will be reintroduced by the sandpaper used to chamfer. This is a very delicate area I find best to be chamfered with a soft polishing wheel at the final step of the project.
After .015″ of the unsupported depth was removed, I stopped filing. Fortunately cartridges still completely entered the chamber. I tend to file slightly uneven so I moved on to squaring the end of the barrel.
Squaring the Barrel
Remove the barrel. Remove the bolt. Remove the extractor. Smear lipstick on the face of the bolt. Cover the breech end of the barrel with black Magic Marker.
Install the bolt (don’t touch the lipstick). Hold the bolt rearwards (using the charging handle) and securely attach the barrel. Release the bolt so it firmly kisses the end of the barrel. Hold the bolt rearwards (using the charging handle) and remove the barrel. Check for lipstick on the barrel. These are the high spots. I refer to this step as “The Lipstick Pattern Transfer Check.” Squaring is complete when the lipstick on the bolt transfers to at least 90% of the barrel.
File the lipsticked areas and try to avoid the black areas as much as possible. Apply a fresh layer of lipstick to the bolt after every 2 or 3 lipstick pattern transfer checks, and re-black the barrel. By the time I managed to get the barrel squared sufficiently, the unsupported area was reduced by another .005″.
To remove the coarse scratches from filing I used 320 grit sandpaper fastened to a firm padded sanding block (Veritas sanding block) until most signs of filing scratches were removed. I then used 400 grit to take care of the remainder. Like my filing, my sanding was a bit uneven so by the time the barrel was sufficiently squared an additional .003″ was removed from the unsupported case area. Overall .023″ had been removed and .008″ unsupported area remained. Fortunately, cartridges still chambered fully by gravity alone.
Chamfering the Chamber
I used 600 or 800 grit sandpaper, and sometimes very worn 400 grit, for chamber chamfering because I tend to overdo things using grits coarser than those. I tape the outside end (Foredom end) of the sandpaper to prevent it from unravelling as it spins.
The idea of chamfering is to break the edge (slightly round-off the edge) at a 45 degree angle. It is very easy to over-chamfer which is why I use a Foredom Tool with a speed-control foot pedal. Refer to the picture “Chamfering the chamber edge” shown above.
In my haste, I made the mistake of chamfering along the thin area of the barrel which quickly induced another .005″ dip into to the unsupported chamber area, which is why I recommend using only the polishing bob in this area.
To remove the entire .013″ remaining the chamber would need to be shortened .036″ overall (originally was .031″ until my .005″ mistake). My mistake irritated me so I decided to take my chances of further shortening the chamber to remove the .005″ mistake. I went back to square one: file the barrel, sand the barrel, square the barrel.
I filed until .005″ was removed then sanded to remove the file marks and square the barrel. .008″ was removed during the process. This left the chamber shortened .031″ overall with a narrow .005″ dip (my mistake) remaining. As proof that God loves me, cartridges still chambered fully by gravity. I decided I’d pushed my luck far enough at this point, so I moved on to the final steps.
I chamfered the chamber using 800 grit and avoided chamfering the thin barrel area. The original factory oval and over-chamfer of the chamber (the 6 o’clock area) was completely removed during the process. I chamfered-in a slight feed ramp on the chamber edge at the 6 o’clock area of the chamber to aid in feeding (see picture “Completely finished product”).
Polishing
I plugged the chamber again with a Q-tip to keep it and the bore free from accumulating polishing compound during the polishing. I used a medium/medium-soft felt wheel charged with polishing compound in the Foredom Tool. A hard felt wheel is a bit too firm for the fibers to get low enough into the chamber to polish the chamfer but a medium/medium-soft wheel will get into the chamber and polish it nicely.
If using a lot of pressure on the bob and moving it from 3 o’clock to 9 o’clock, it is possible to polish the thin area of the barrel to the point of inducing some unsupported area. In the picture “Finished Product: Unsupported case area removed” below you may be able to see the slight dip that was induced from too much downwards pressure on the polishing bob. Soft pressure and moving the polishing wheel from 6 o’clock to 12 o’clock reduces that possibility. Go slow, be cautious around the thin chamber area, and check progress often.
A mirror-like finish on the end of the barrel and a glassy-smooth chamfer around the full diameter (360 degrees) of the chamber was achieved.
It’s pleasantly noticeable how smoothly cartridges with both lead and plated bullets now enter the chamber. I also lightly polished along the sharp edges on each side of the extractor groove on the barrel and polished-in a chamfer around the full diameter of the barrel shroud bevel to make for a nicer final product. It’s always good to smooth the edges on things that may cut your skin and clothing or scratch other equipment.
When I worked on my friend’s Henry US Survival barrel to remove its unsupported case area I used a different method to polish the chamber chamfer. I used a hard, tapered felt charged with polishing compound in the Foredom tool. All went well and in a few seconds the chamfer was glassy smooth.
Because the tapered cone polishes the full diameter of the chamber edge it is also polishing the thin area of the barrel. Again, I applied too much pressure as it spun and created a .003″ dip to the unsupported area – another mistake to learn by. Using a softer tapered bob would be a quick and effective way to polish the chamber chamfer glassy-smooth.
When polishing was complete, I cleaned the bore, the chamber and the outside of the barrel to remove any polishing compound residue, then lightly oiled all areas.
The final step: Test firing
Test firing is mandatory after any type of chamber work and I was confident things would perform well based on my tests in the shop. Forty cartridges were fired and proved the repair successful and accuracy was as good as before. When my gun was done, I removed .021″ unsupported case area from my friend’s US Survival using the same process explained in this article. I did not remove the whole .031″ it had because I would like to use a lathe to fix his nicely. This way I have .010″ “room-to-lathe” so to speak. His gun also test fired successfully, and he’s happy.
Conclusion
My repair process may not be the quickest, easiest, or the best way, but it did prove it can be successfully accomplished with basic tools, basic equipment and minimal supplies, if that’s what you have.
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