Thoughts on this please

Ok, I did not catch that the cases pictured had never been fired but this once and never resized and now they look like emminent case head seperation.

Only 2 things I can think of.

1) Your rifle has a headspacing issue and headspacing should be checked before anymore firing.

2) That brass if not purchased new, may have been fired before 2 or 3 times?? How sure are you the cases were brand new?
Positive they are new, in a sealed Peterson box.
 
I would also look at the xc. I have three of them, all on short actions. One each 7, 7.5, and 8 twist. All longer throats
Shoot bergers out of all of them and all will shoot 1/2 moa at distance. I shoot these out to 1K

115 Vlds out of the 7 T at 2960 fps
105 vld out of the 7.5 T at 3070 fps
105 vld out of the 8 T at 3150 fps
Every thing Ive killed with these have been one shot kills ...mule deer, whitetail and a 400 lb black bear at 150yds. Bear dropped and didn,t even twitch.
I could shoot 115s out of all of them but ended with a bunch of 105s and really like how they perform

As I said, I haven't had that issue, and I own a few belted cartridges and have been loading them for nearly 5 decades.

I even have one of Larry Willis' belted magnum collet resizing dies for those case bulging issues, but I have yet to use it.

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Same here, I had Willis die for a decade and never used it through half a dozen 7 mags, custom, and factory.

Lots of NONSENSE keeps getting repeated on the net about belted magnums. If a Non Truth is repeated often enough, then it is accepted as truth.

I would have the OP's chamber inspected by someone that has a bore scope. as it looks to have a scratch in the chamber.

On many chambers, if you only bump the shoulder back .002, you may not reduce the dia in front of the web enough to chamber the round when the case needs full-length sizing. Often you have to bump back the shoulder quite a ways so the case is actually full-length sized. When you have no choice you will get a bit of case stretch where the case may have to be discarded after 8 firings or so.

I started reloading the 7 mag and 300 Win mag in 1978 and never had a problem with belts in Rem 700s, Savage, Browning, and customs. Guys that are NOT advanced reloaders that have problems with a belted magnum, always blame the belt when it is their lack of knowledge that is really the problem...production dies and factory Chambers. Small base sizers per caliber often solve a lot of problems as mis matches between Factory chambers and production dies vary greatly.

The problem in the OPs chamber looks like the reamer picked up a chip that scored the chamber, and with a small mini mag flashlight with the bolt open, if you spin the rifle around on the muzzle, look in the chamber, you may actually see the imperfection. I am assuming that the scored section on the brass happens on every case in the same place, no matter what brand of brass you use.

If you have a headspace problem, often a ring will start manifesting itself partially around the circumference of the case. Some think that a "case stretch" ring will go all the way around but that is not the case many times. Then the case will separate on subsequent firings. You will extract a case head, insert a pistol cleaning brush into the part that is stuck in the chamber, and the case will come out with no effort exerted.

You should quickly and with little effort be able to determine if the chamber is scored with the small flashlight.
 
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If you had case head separation previously, yes, you can have a carbon buildup in the chamber that will mark your new brass. Been there.
A good carbon removal should fix you up.
My stw brass moves .018" after the first firing and I don't get heads coming apart once I learned how to bump the shoulder.
 
Same here, I had Willis die for a decade and never used it through half a dozen 7 mags, custom, and factory.

Lots of NONSENSE keeps getting repeated on the net about belted magnums. If a Non Truth is repeated often enough, then it is accepted as truth.

I would have the OP's chamber inspected by someone that has a bore scope. as it looks to have a scratch in the chamber.

On many chambers, if you only bump the shoulder back .002, you may not reduce the dia in front of the web enough to chamber the round when the case needs full-length sizing. Often you have to bump back the shoulder quite a ways so the case is actually full-length sized. When you have no choice you will get a bit of case stretch where the case may have to be discarded after 8 firings or so.

I started reloading the 7 mag and 300 Win mag in 1978 and never had a problem with belts in Rem 700s, Savage, Browning, and customs. Guys that are NOT advanced reloaders that have problems with a belted magnum, always blame the belt when it is their lack of knowledge that is really the problem...production dies and factory Chambers. Small base sizers per caliber often solve a lot of problems as mis matches between Factory chambers and production dies vary greatly.

The problem in the OPs chamber looks like the reamer picked up a chip that scored the chamber, and with a small mini mag flashlight with the bolt open, if you spin the rifle around on the muzzle, look in the chamber, you may actually see the imperfection. I am assuming that the scored section on the brass happens on every case in the same place, no matter what brand of brass you use.

If you have a headspace problem, often a ring will start manifesting itself partially around the circumference of the case. Some think that a "case stretch" ring will go all the way around but that is not the case many times. Then the case will separate on subsequent firings. You will extract a case head, insert a pistol cleaning brush into the part that is stuck in the chamber, and the case will come out with no effort exerted.

You should quickly and with little effort be able to determine if the chamber is scored with the small flashlight.
As I look at the photos again really closely I notice the ring is not 360 around the whole case, so it may as you suggest be some defect in the chamber scoring the case only in one place likely when it is rotated and extracted.
 
The mark is only about 40% around the circumference and is at the exact location as the case head separation. Had to use JB weld stuffed into the case remnants in chamber to remove it. I don't recall is the mark was there before that happened and I cannot attest to how well it has been cared for, not my rifle. Now was the mark there when new and it contributes to case failures or at least will contribute to future case failures by weakening that area of the case? I was concerned with the previous cases when they started showing marks like this and I figured it was a stretch mark due to oversizing. Rifle still shoots well. Then the case head separation happened so I told the owner need to get new brass and sorted the loaded rounds, separating out the ones I thought might be impending failures. Told him not to shoot them. I pulled bullets on a couple of them and checked the case inside with bent paper clip and they were fine (?). So I reassembled and they were fired without issue. But one of the other ones I fired to shoot them up partially separated so I quit shooting them, took the last 6 apart and discarded all that brass. The case in picture is one of the 100 Peterson he bought at my suggestion when they were available last fall I think.

I was mainly curious of the case separating could cause pitting or damage to the chamber and that is what is causing the mark. I don't use cleaning solutions that are harsh enough to damage the barrel, I don't think I do anyway, maybe he left something in there after cleaning.
 
How hot are the loads you are shooting? Just curious.

Really think its the rifle chamber scored or headspacing or both.

Bit does brass w lighter charge weight look the same?
 
I just don't know how a reamer could cut a proper belt groove, but a grossly deep chamber.
Because reamers have tolerances like anything else. All it takes is getting a chamber cut with a new tool vs a worn tool. Factory will always lean on the side of being long enough and not too short. The shoulder portion of the reamer cuts a lot more metal than the belt portion does, 10x moreso if they aren't using carbide roughers.

There are surprising +/-0.003 variations between "identical" reamers pretty often. Throats are the most likely place to be off mainly, those can be full 0.010" or more off.

This whole mess looks like normal tapered inner wall case fitment to me. Same thing like the lines I get on my 30-06 above the case web.
 
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How hot are the loads you are shooting? Just curious.

Really think its the rifle chamber scored or headspacing or both.

Bit does brass w lighter charge weight look the same?
Not really hot, 64.9g IMR4831 nos 168 ABLR Vel 3003. Also recently tried 7828 and 7977 because that is what I had on hand and didn't have IMR4831. With the Peterson brass I backed off the powder to 64. I have just got an 8# of IMR4831 since the rifle seems to shoot well with it.
 
Nope, this is a common problem with belted magnum cases.
I had the same issues on my .300 WM.

Advice I got here was to bump the brass shoulder down .002 each time I reload them. What's happening is you are over compressing the whole case down onto that belt each time, and then when it is fired, it stretches it back out right at above the belt. It will metal fatique there in 3 firings or so, and you will have case head separation. Bump only the shoulder down and set the die not to press the whole case body down onto that belt.

You can also of course neck load your belted magnums, but many here and Eric Cortina believe that is not as accurate as full case resizing.

So, you do full case resizing but only to the extent, your shoulder bumps down .002 each re sizing.
All good advice, also before you bump the shoulder back, anneal the neck and shoulder so any streching should be up at the shoulder and not back at the web.
 
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