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Posted: 6/7/2020 11:52:33 AM EDT
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I have a cheap .300 Blackout upper and am pretty consistently seeing marks on the spent brass that I think are from a burr or rough spot in the chamber. Haven't had any extraction issues but I just started reloading for this caliber and would like to maximize the life of my brass. Is there a reasonable and effective way I can polish the chamber a bit without taking it to a gunsmith? Appreciate any advice |
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Some 320 or 400 on a dowel, cross hatch gently . I have drilled and tapped the primer hole of a fired case and put a rod in it, chucked it in a drill and used polishing compound to smooth out a really rough chamber on a rifle I was having extraction issues with. Still shooting the rifle ten years later. 
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Quoted: Some 320 or 400 on a dowel, cross hatch gently . I have drilled and tapped the primer hole of a fired case and put a rod in it, chucked it in a drill and used polishing compound to smooth out a really rough chamber on a rifle I was having extraction issues with. Still shooting the rifle ten years later. That is rather coarse. 600 and up. Use a split dowel and a variable speed drill. A few seconds at medium speed to start. |
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Yes, bbl. extensions can drag a scratch on the side of cases; and they are quite deep. So with the bbl. out and in a vise, I use a Dremel tapered Cratex bit to breaks all the sharp edges inside the extension as best that I can. It is usually the lugs on the extraction side that are the culprits. The lug edges are sharp as a razor, and this leads to stress risers on the extracted case. Not good for longevity. |
Also, Brownell's has a Flex-hone abrasive brush for the AR chamber. I think mine is 800 grit. It will polish but not remove any real metal. But I would look at the sharp corners inside the extension first. Get rid of them and if the issue still comes up, then think about the chamber. Not likely though.
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Quoted: Also, Brownell's has a Flex-hone abrasive brush for the AR chamber. I think mine is 800 grit. It will polish but not remove any real metal. But I would look at the sharp corners inside the extension first. Get rid of them and if the issue still comes up, then think about the chamber. Not likely though. https://pbase.com/packrat/image/171022633.jpg Wow, I never knew they made those. I might have to pick one up in a couple calibers. In the past, I have used a old bore brush wrapped in some fine steel wool and soaked in some hoppies No 9 to clean/polish a mosin nagant chamber that had sticky extraction. I have also uses a 45 cal bore mop slightly wetted with some hoppies and some JB bore paste on a rough 308 win chamber. It helped a little, but the JB was just not rough enough. |
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I had a sharp spot on 300 BO barrel that was giving me some consistent scratches. I took a .410 bore swab, loaded it up with some of the white polishing compound you'd use on a bench grinder, and then chucked that in a drill. As slow as I could, I polished for maybe 60 seconds. Cleaned it really good with Hoppes and another clean bore brush, and then compared results. If you do any chamber polishing go really slow..hard to put metal back on once it is taken off, even at the .00001" level. |
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