Bur in chamber

[kilotanker22]

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.

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

[kilotanker22]

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

[kilotanker22]

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.

[kilotanker22]

I was able to remove what I thought was a bur. It was actually a sliver of brass. The chamber is pretty well polished and smooth.

Still resized brass will not chamber without forcing the bolt closed. I measured the area in front of the belt. My largest measurement was 510 on the piece of brass that I measured. At that measurement I should not have trouble chambering the brass. Some pieces go easier than others. But most are very tight.

Could it be a head space problem? Maybe my die is not setting the shoulder back far enough?

[pwc]

Could it be as simple as with the obstruction removed, you trimmed the brass a little long a d with the bullet in it won 't fit the throat?

[kilotanker22]

Don't think so. The brass is trimmed to 2.485".

I think that I discovered the real problem. I am using an old die set from RCBS that calls for shell holder #4.
I had shell holder number #43. Which will work with newer die sets, but that's the shell holder for the wsm.

I replaced it with shell holder #4 and reset the die. Same problem but better. Set the die to make firmer contact with shell holder. Showed more improvement.

So I ground off about .002 from the shell holder. Reset the die. And they chamber fine now.

[Onward Allusion]

Dremel

[4V50 Gary]

No dreaded high speed spinning tool.

[Doyle]

I think I would make up a wood dowel wrapped in 1000 grit autobody paper and just polish it out.

[kilotanker22]

Originally Posted by Doyle

I think I would make up a wood dowel wrapped in 1000 grit autobody paper and just polish it out.

I used a scotch brite pad cut into strips. put them through my patch eyelet and spun them with my hand drill. it cleaned it up pretty well. There is still one little spot where the belt enters the chamber, but it does not seem to be affecting anything now.

I think That I will just shoot this barrel until I save the cash for a new Barrel. I live in PA So I will probably send it to Shaw to have it trued and rebarreled. I called them last week and they said like $600 total for a new barrel, the work and return shipping. I think thats pretty fair considering some barrels cost that much alone.

[Kapusta]

Late to the party, but - belted cases headspace off the belt, i.e., the belt doesn't even enter the chamber. Have you taken a look at your bolt face?

[kilotanker22]

I got it all figured out. Got the extra material and a bur out.

The problem ended up being the area in front of the belt was expanding too much. Even after the first firing not wanting to chamber. I bought a special die to re size that portion of the case and problem solved.

[Unclenick]

Another Larry Willis die finds a home.

[hooligan1]

I use a Forster Bonanza Benchrest full length sizing die for my 7 mm Rem mag.
My Larry Willis die just sets on the shelf.
Kilotanker I'm glad you got that figured out.
7 mm rem mag headspaces off the belt the first time it's fired, after that firing it headspaces off the shoulder, if you don't believe me measure factory ammo before and after firing, and then again after sizing.
7 mm Remington Magnum is one of my top 3 cartridges I love, and load regulary.

[kilotanker22]

Originally Posted by hooligan1

I use a Forster Bonanza Benchrest full length sizing die for my 7 mm Rem mag.
My Larry Willis die just sets on the shelf.
Kilotanker I'm glad you got that figured out.
7 mm rem mag headspaces off the belt the first time it's fired, after that firing it headspaces off the shoulder, if you don't believe me measure factory ammo before and after firing, and then again after sizing.
7 mm Remington Magnum is one of my top 3 cartridges I love, and load regulary.

I do in fact believe you. They grow .019" from virgin brass or factory ammo. My 300 win mag grows .015.

[Unclenick]

That's because SAAMI has the dimensions set up to ensure new brass headspaces on the belt. In order to guarantee the cartridge seats on the belt before the case shoulder can arrive at a chamber shoulder of any tolerance, they have to make the case shoulder extra short. As Hooligan1 says, though, once fireformed to your chamber, you can size to headspace on the shoulder to extend brass life.

[F. Guffey]

Could it be a head space problem? Maybe my die is not setting the shoulder back far enough?

I do in fact believe you. They grow .019" from virgin brass or factory ammo. My 300 win mag grows .015.

They grow? You started out wondering if the die is setting the shoulder back; and I wonder how the die sets the shoulder back and I also wonder how the shoulder moved forward .019". Both cases have belts meaning the case cannot move forward after the belt seats.

I have almost given up on reloaders being able to understand the sequence of events the case goes through when fired. The worst thing that can happen to a case when fired is for the shoulder to move forward (beyond comprehension)m the case is held to the rear of the chamber by the belt. If the case is held to the rear of the chamber the shoulder can not move forward; unless the case stretches between the shoulder and belt. And that is the beginning of case head separation.

Bad habits? If the reloader increases the distance between the shoulder and case head the shoulder of the case will head space on the shoulder of the chamber. Meaning? The case does not move forward, if the case does not move forward the case does not head space on the belt. When that happens the area in front of the belt is not supported, I am the fan of less head space on the belt but manufacturers of belted cases do not make cases with thicker belts and that goes back to my comment; "Component manufacturers do not make cases for reloaders that know what they are doing".

F. Guffey

[F. Guffey]

And then when it comes to something in the chamber, my cases are embeddable, If I have a nice, smooth clean chamber cases fired in that nice, clean smooth chamber will not have foreign matter embedded in the case nor will the case have dents showing artifacts of matter in the chamber. It is like anomalies, when fired the case will show matter in the chamber that is not normally there.

F, Guffey

[Unclenick]

Agree with you on the belt tolerances. If I were setting up a belted magnum gun today, I would get a chamber reamer made with no belt portion. I would buy a supply of brass and cut the belt recess in the chamber separately to get tight belt headspace on that particular brass and then finish the chamber to have its shoulder kiss the case shoulder coincident with belt seating. It would be some bother, but that is what lathes and boring bars are made for. If I ever had to get more brass, I might have to face adjusting the chamber, but 250 cases treated well and never stretched appreciably should last the life of the barrel. A little powder capacity would be lost without the shoulder inflation occurring, as expanded case volume determines peak pressure. But I should think it a worthwhile tradeoff. It just wouldn't be suitable for digesting some commercial ammunition.

[F. Guffey]

It just wouldn't be suitable for digesting some commercial ammunition

.

I can only guess there is someone out here that insist the belt is necessary. If in your efforts you built a rifle with out the belt at the rear of the chamber it would be easy to purchases magnum cases and then remover the belt. And while you are doing 'it' you could purchase magnum cases that are too long for the chamber from the shoulder to the case head. Nothing like forming first and then firing.

F. Guffey

[Old Stony]

I had that same problem many years ago with an identical rifle in that caliber. I called the company and they told me that factory ammo would fit is it was sized to smaller dimensions, but reloads could be a problem. I found a set of small based dies and never had another problem.