Remove burr in chamber

[Kilo-OG]

Hello,

Recently I acquired an Interarms mark x in 7mm remington magnum. Shoots ok, But I have noticed that after only one firing New brass is difficult to chamber. Now This is after Sizing and trimming. Also after verifying that the area in front of the belt is not swollen. Still measures .510-.511....

The rounds definitely still chamber, but some with a good bit of resistance. Being that The area in front of the belt had not yet grown out of the acceptable range. I figure the brass must be hanging up somewhere else.

So I resized a piece of once fired brass, trimmed and what not. Then seated a bullet to make a dummy round. Colored the entire thing with a marker. And the chambered the round.

The only marks on the dummy round were from the magazine and shoulder where it was dragged across the ramp to load.

The only other spot That marker was worn off was a small spot on the belt itself. I also noticed that it not only removed the marker in that spot, but also removed a very small amount of brass from the belt in that spot only.

So I got out my bore light and after careful observation I found what I believe to be a bur in the chamber. Right where the belt of the case sits into it. It is not large, but when looking at the right angle it is visible.

What is the best way to remove this?? I have seen a person once before use strips of sand paper in a cleaning eyelet and an electric drill. I guess that would be ok, but I am sure the masses here have a better alternative.
I intend to re barrel this rifle in the future anyway, but would like to continue shooting it for now... I don't see any sense in replacing a barrel that shoots ok sooner
if I don't have to

I was thinking also maybe I could use a small amount of lapping compound on a fired case. I could tap the end of the case and use a cleaning rod to spin it in the chamber.

Thanks in advance for any insight.

P.S. I would post a photo, but there is no way i will be able to get it to focus so you can see

 

[john323]

Try JB board polish. It can be purchased through Brownells. Non imbedding.

 

[mrmeval]

Try JB board polish. It can be purchased through Brownells. Non imbedding.

There is J-B® NON-EMBEDDING BORE CLEANING COMPOUND

And there is J-B® BORE BRIGHT

 

[Old Shooter]

Sounds like a good plan. I'm just curious how long this may or may not take. The brass case being softer than the steel particle you are trying to smooth out it seems that the larger share of metal removal would be on the brass case side of the game. I suspect it will work but I wouldn't be surprised if you went thru a few cases to get done. Will be interesting to hear how it works out.

 

[Blue68f100]

That or maybe some Cratex polishing abrasive wheels. I've used these type of abrasives over the years for removing burrs.

https://www.cratex.com/Products/Rubber-Abrasives

 

[4v50 Gary]

I'd rather get a finishing reamer and hand spin it without any downward pressure. I'd hate to get a divit where the burr was.

 

[tark]

Don't go near it with a dremel! Even with a soft cratex wheel. Or an MX wheel. Both of those can remove metal if used improperly. Dremel's do have uses in gunsmithing, but doing anything to a chamber isn't one of them.

 

[Shimitup]

I find it odd that the factory reaming job left a burr. Just though you might want to make sure that a scope thread wasn't drilled and tapped too deep.

 

[BBBBill]

Just though you might want to make sure that a scope thread wasn't drilled and tapped too deep.

^^ The OP has not stated exactly where the burr resides. If it is TDC, then I am inclined to agree with Shimitup.

 

[edwardware]

. . . a small spot on the belt itself. I also noticed that it not only removed the marker in that spot, but also removed a very small amount of brass from the belt. . .

I can't imagine a burr sticking into the belt area unless it's been knocked in by an impact to the barrel face; look for a corresponding dent.

Edit: or as @Shimitup said, an overdrilled scope mount hole.

If you can locate it. . . you probably can't grind it without gouging. Maybe use a hard, smooth tool to burnish the burr back into place? I've used the smooth end of a chainsaw file for similar burnishing jobs. You don't want to cut material, you want to push it back where it came from.