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I have a SAI made 18.5" take off barrel that I am considering using on a new build. I had used it before with an SAI bolt, but had issues with cases sticking in the chamber.USN4 I can see reamer marks in the chamber.USN3 But it feels rough in about the last 1/2" or so before the shoulder. I used a plastic dental pick type tool to see how smooth the chamber is, and I feel quite a bit of roughness at that spot.USN3 All around the chamber.
I have a lathe and can spin the barrel to polish it. My question is, what grit emery cloth/paper should I use to polish?
 

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Tread carefully!

What happens if you polish it too much? Now you have a custom chamber size.

I would start with bore lapping compound, just to shine it up. Maybe hit it with 600 grit paper, for a couple of turns.

But don't listen to me - get one of our experts to answer. Hate to see a ruined barrel.
 

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Good question. I hope some one will give a good answer. I had not thought about spinning the barrel to polis the chamber. For some reason I had pictured a swizzle stick with a rag in it powered by a die grinder.
 

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The two commercial hones are 400 and 800. Sounds about right to me without removing too much material. MAYBE a QUICK hit with some 320 in a local area if exceptionally rough.

http://www.brushresearch.com/brushes.php?c2=183

[ame]http://www.amazon.com/Brush-Research-09259-Flex-Hone-7-62X51mm/dp/B00DB8E8ME/ref=sr_1_1?ie=UTF8&qid=1387392363&sr=8-1&keywords=Flex-Hone%C2%AE+for+Rifles+7.62[/ame]

[ame]http://www.amazon.com/Brush-Research-09260-Flex-Hone-7-62X51mm/dp/B00DB8E9J6/ref=sr_1_2?ie=UTF8&qid=1387392363&sr=8-2&keywords=Flex-Hone%C2%AE+for+Rifles+7.62[/ame]
 

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The master gunsmith I use for all my gunsmith needs has always told me to never polish the chamber against the direction of the cartridge case movement. I have always put the polishing compound or sandpaper in the chamber and spun it, but he told me to polish in the direction the brass will move. He said if you have even microscopic scratches in the surface, they can resist the movement of the brass once it has expanded after igntion since the scratches would be 90 degrees to the movement of the brass. He uses a magnifying eyepiece when he looks at chambers. The kind of eyepiece a jeweler wears in one eye. So, he had me take some 600 grit sandpaper and put it around a dowel that was the right diameter and move it in and out of the chamber as I moved around the circumference of the chamber. I have done it like that since, and it works better. Another trick he showed me was to put polishing cream on cartridges and let it dry, and then fire them in the weapon. You have to clean the chamber periodically. I have done this with .22LR and it worked well, and it worked well with 9mm and .45ACP, but I have not tried it with .308 or .30-06. Might get expensive shooting the larger calibers, so you might just want to use the sandpaper and dowel technique.

Charles Tatum
Alamo Professional Arms
 
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