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I have a m91/30 that I believe has a burr in the chamber. After firing a round, the extraction is very hard. In fact, the first round I fired, I had to put a block of wood against the bolt and bang on it to extract the cartridge. The cartridges all have scratches about 1/4 inch long near the base of the cartridge. I can cycle unfired cartridges all day with no problem. After firing and the cartridge expands, they are very hard to extract. I will post pictures when I get home tonight.

I have yet to disassemble the rifle but would it be possible for me to simply polish the chamber area? If so, what would I use? Sandpaper? steel wool? brake cylinder hone? I have all sorts of tools and options, I just don't know which would be best. Obviously, I would not want to remove any more then necessary. The nearest gunsmith in my area is over an hour away and not convenient. That is why I would like to try it myself. Only paid $85 for the rifle so I'm not out too much if I screw it up either. For such a cheap rifle, I don't want to take it to a gun smith and end up spending more on fixing it then the gun is worth.
 

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Do you mean a 91/30? In my limited experience,scratches on a case don't necessarily come from the chamber,they could be caused by something in the magazine well or by the ejector even,.Stiff extraction could be from a dirty or rough chamber sure enough but the ejected case would show this.
you also don't say what type of ammunition you were shooting ,surplus,factory steel cased,or reloads? Hot loads or over length brass could also cause stiff extraction.
 

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Yes, I meant m91/30. typo in the title. I am using surplus copper washed steel cased ammo - might be Romanian. I'll check when I get home. The scratches only appear if I fire the ammo. I can cycle unfired without a problem. To me this says that it has to be something in the chamber that is rubbing after the cartridge has expanded from firing. If it was from the magazine well it would occur when cycling unfired ammo. Additionally, the scratches begin about 1/8 inch above the rim and are about 1/4 inch long. To me, that seems too far up to be an extractor related problem.
 

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Could be the ammunition.Steel doesn't shrink back as much as brass cased does. If you have access to different ammunition try some ,brass cased preferably.Are these scratches going around the case or the length of the case?
in my limited experience,you can poilsh a chamber ,but just a little , 600 grit wet /dry or emery cloth on the end of a split dowel that is smaller than the chamber ,by hand, no power tools.a little at a time. But trying different ammunition might be the first thing to do.
 

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Discussion Starter #5
I measured the diameter of the casings before and after firing.
BEFORE: 1.215cm
AFTER: 1.225cm
When trying to cycle spent casings, they take considerable force to get back in the chamber. The majority of the expansion only occurs near the base of the casing. The scratches are also right on of the expanded part. The expansion might be part of the problem but the scratches are still cause for concern. here is a picture.

 

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I would guess that anything you can do is only going to make matters worse,if you are attached to the gun take it to a professional,otherwise sell it for parts.Course that is just MY opinion ,someone who is more versed in the Mosin might see it different.
 

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Welding spatter

Good news! by following the information found in the following article, I fixed the problem.

http://www.surplusrifle.com/articles2008/mosinburr/index.asp

That is what I found in my 91/30 chamber! I was removable using a tiny screwdriver, then a small brake cylinder hone. Works great now. Its a 1921 barrel version. I was able to get 100 yd groups of 4 inches during the last group. It was the first time that I used the rifle. The session was 5 cartridges, in each of 5 rounds. The last was the best.
 
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