Thoughts on this please

[MagnumManiac]

Wow. Has to be a rifle related head spacing problem or a defect in the brass ductility, and Peterson has a good reputation.

I use only it and Lapua myself.

Id check headspacing for sure.

Wow, there is NO headspace issue…just because there is a scuff on the brass that LOOKS similar to a head separation does NOT make it so. Looks to me, and I have seen hundreds of chambers with a Hawkeye scope, that a piece of swarf was caught in a flute of the reamer and made a mark before exiting the flute, it is NOT deep enough to cause an issue but can be polished out in a few seconds with scotch brite.
To the OP, the belt recess is part of the reamer, it is cut at .220" or a 'thou less by good 'smiths. It rarely ever poses a problem of excess headspace and this is NOT your issue.
It could also be a faint gas cutting mark from a case head separation, but this is unlikely as they occur when the case shrinks back from being forced against the chamber wall, not from expansion as many will tell you as gospel.

Cheers.

 

[Tulsa Reiner]

I feel like there is a simple answer. It may not be the answer you want, but the bore scope is sure going to eliminate a lot of variables.

(Not to side track):
Bore scopes are worth their weight in gold, just a little gold. I would recommend the Teslong with ability to connect to your smart phone by blue tooth and take pictures, both videos and stills. This is a great way to compare before and after your cleaning efforts.
Beware of getting side tracked by minor imperfections in the barrels you inspect. You will be impressed by what you see.
I mainly use mine to detect carbon rings.

 

[FEENIX]

Wow, there is NO headspace issue…just because there is a scuff on the brass that LOOKS similar to a head separation does NOT make it so. Looks to me, and I have seen hundreds of chambers with a Hawkeye scope, that a piece of swarf was caught in a flute of the reamer and made a mark before exiting the flute, it is NOT deep enough to cause an issue but can be polished out in a few seconds with scotch brite.
To the OP, the belt recess is part of the reamer, it is cut at .220" or a 'thou less by good 'smiths. It rarely ever poses a problem of excess headspace and this is NOT your issue.
It could also be a faint gas cutting mark from a case head separation, but this is unlikely as they occur when the case shrinks back from being forced against the chamber wall, not from expansion as many will tell you as gospel.

Cheers.

I have a similar take on it and responded as such in #4, especially for new brass and only on a particular spot.

 

[Mike D Texas]

Wow. Has to be a rifle related head spacing problem or a defect in the brass ductility, and Peterson has a good reputation.

I use only it and Lapua myself.

Id check headspacing for sure.

Based on one of his earlier posts it appears his brass is growing .015" which to me indicates a deep cut shoulder datum. Only way around that is to fireforming loads to his chamber with a mild load and bullet jammed in the lands.

Then he can start his usual FL resizing and appropriate shoulder bump.

 

[Philward]

Morning guys. Quick update, since I don't have a borescope(yet) I took a piece of 12g copper wire and bent a right angle in the end, put it in the chamber and moved it back and forth to feel for roughness. At the 7 o'clock point there is an area of roughness just up into the chamber, does not go around the circumference very far. I'll try to reach in with something and clean it up. Can't really look into the barrel to see it.

All of these 50 Peterson cases have been fired at least once in the rifle, annealed and sized correctly. I will respond back if I get the roughness out of chamber.

 

[Veteran]

Morning guys. Quick update, since I don't have a borescope(yet) I took a piece of 12g copper wire and bent a right angle in the end, put it in the chamber and moved it back and forth to feel for roughness. At the 7 o'clock point there is an area of roughness just up into the chamber, does not go around the circumference very far. I'll try to reach in with something and clean it up. Can't really look into the barrel to see it.

All of these 50 Peterson cases have been fired at least once in the rifle, annealed and sized correctly. I will respond back if I get the roughness out of chamber.

Yes, you can try cleaning but I would check it before and after w a borescope. Any gunshop will have one.

 

[Mike Matteson]

I have written on this before. I would get case separation in 3 firing with my belted mag. I switch to neck sizing and that stop the case separation in it's tracks. Bumping the should only .001 or 2 should work. I haven't try that yet. I know the Match shooters are saying FL sizing. They are shooting match not hunting. I never been to a match shoot, but from what I read they aren't using belted mag case anyway. I went as far as only partly neck sizing my belted mag. If I note that the bolt is getting hard to close then I FL size them.
A borescope is needed. That would cut the guessing out of what going on.

 

[VinceMule]

One thing that is almost universal now with serious match shooters is the full-length sizing of their cases. I found this to be true with my custom and factory 7 mags with Remington and Winchester brass with very tiny groups resulting.

Like Mike Said, the neck sizing stopped the case head separation in 5+ firings. Neck sizing may produce various amounts of pressure needed to close the bolt on loaded rounds and flyers out of the group is part of the process of inconsistent pressure needed to close the bolt. Forster neck sizers are made in such a way that you can bump the shoulder back with their Neck Sizers, and no other brand of neck dies will bump shoulders until you get into custom dies. The inconsistent amount of pressure needed to close the bolt which produced flyers was a hard lesson learned..

 

[Mike Matteson]

One thing that is almost universal now with serious match shooters is the full-length sizing of their cases. I found this to be true with my custom and factory 7 mags with Remington and Winchester brass with very tiny groups resulting.

Like Mike Said, the neck sizing stopped the case head separation in 5+ firings. Neck sizing may produce various amounts of pressure needed to close the bolt on loaded rounds and flyers out of the group is part of the process of inconsistent pressure needed to close the bolt. Forster neck sizers are made in such a way that you can bump the shoulder back with their Neck Sizers, and no other brand of neck dies will bump shoulders until you get into custom dies. The inconsistent amount of pressure needed to close the bolt which produced flyers was a hard lesson learned..

I stumble across this on to this in the late 90's. The other part of this is I shot a 308NM. The shoulder length is shorter than the 300WM case, and the neck is longer. Trying to get 308 NM neck sizing die good luck. A years more. So changed to a 300WM neck sizing die. It only sized about 3/4 of the neck on the 308NM case. I do have them now.
I also started to weight the cases and changed to Win Cases. Found them to be lighter. I had several hunderd of 300WM cases. So I group them with a grain or two groups. All at the same time it stop my case separations. Only lost case do to primer pockets after that, and neck splitting. Got that fixed with annealing one time. Simple, but not what I do as of today. I have done much in load development in a long time. Once I find load that I like or happy with that's it. That what I use going forward with that rifle. I am not into tonnage for bullets. The heavest is 200gr in my 338WM @ 3220fps. 500 yds has been my limits for range.
I now looking at the 6mm/2890AI to extend that range to 700+ yds. It's brand new to me and there isn't much out there on loading. That find with me too. Something I can work on and develop loads for it. I did sent you how I going after the loading process. I do have QuickLoad disk.
I just need to my reloading shack that I need to build. That will start in about 2 weeks. My son the dentist is working over my teeth presently and getting even with me for when he was a kid and I was the old man.

 

[VinceMule]

I anxiously await your results, and I am sure that it will be stellar!

 

[Philward]

Couple questions on this reloading belted Magnum cases. If the belt isn't contacting the chamber and the shoulder is contacting the chamber, what will happen when it's fired? And the opposite, if the belt contacts the chamber but the shoulder does not? Does headspace off the belt mean there is 1 or 2 thousandths space between front of the belt and chamber belt notch? Should there be less clearance at the belt than at the shoulder?

 

[VinceMule]

"Does headspace off the belt mean there is 1 or 2 thousandths space between front of the belt and chamber belt notch?"

This is correct, and the amounts can vary somewhat up to .005 and can be more. Unless specially ordered by the gunsmith, Head Space gauges for belted mags are always off the belt.

Using a 35 caliber ogive gauge with dial caliper, you can measure the headspace of new unfired brass and then how much it grows after it is fired.

My 7 Rem mags and 300 WM loved an accuracy node right up at the top of the pressure curve, so brass usually lasted 5 firings on Rem brass and more on Winchester.

Lots of BS out there on sizing, but bottom line, you have to size enough of the Web where the bolt closes easily, but not too much. So, using the ogive gauge you can set some standards for a particular chamber

New brass headspace length Fire formed length Tight extraction length Neck sized length with Forster Neck sizer
Minimum and Max in the lot needs full length sizing bump shoulder .002 or more

The other can of worms is web dia, and BS abounds in internet lore on this issue. BS repeated becomes gospel truth. Many of the top gunsmiths in the country design proprietary reamers based on the Web dia, Shoulder dia, shoulder length, neck size, freebore dia, etc.

Today, the most ignorance lies in web dia of the new brand of brass that you are using vs the Reamer dimensions with production dies that vary. Realize that all reamer makers have a +/- tolerance of 0.0005 in their grinding, so you can get a smallish reamer or a slightly over size. Having problems often leads to a chamber cast with cerrosafe vs just ASSUMING that the reamer print is correct.

Many people send in their dummy rounds to the reamer maker and have the reamer maker make a reamer off of those several pieces of brass. The employee of the reamer maker may or may not be aware of the tolerances needed between the web of the case and the reamer for proper extraction, focusing on the neck dia, freebore dia, and freebore length for the dummy round supplied.

Many of the most successful gunsmiths in this country will take new brass, add a minimum of .0034 minimum for a hunting round, and match shooters may run a tighter .0023 over new brass dimensions. Recently in a conversation with two very experienced gunsmiths and National Match shooters told me that they add .005 and as much as 0.010 over new brass dimensions in order to not get Premature pressure signs with its related extraction issues.

I have personally experienced over size NEW brass issues with many of the Lapua cases, Norma cases, and RWS that are larger in the web vs their USA Saami spec counterparts. Peterson, AGD, and Alfa all have their web dimensions often different. So, the advanced reloader has to be aware of their Web dimensions and adapt accordingly.

New brass web dimension fully formed web dimension Max web dimension that needs full-length sizing

There is more than a double barrel butt load of bad information on Web dimensions in Super accurate long-range hunting rifles.

You need a micrometer that measures to 0.0001 to measure web dimensions as any machinist will tell you, never trust dial calipers and I have all the best....trust me on this issue. A $39 I-Gauging micrometer & Shars is well worth the money spent(ebay). I like the mechanical digital as they are harder to make a mistake reading. A reloader does not need a mic that measures to the 0.00001, and I would not advise you to spend money on one of these electronic mics as the first time you drop it, the electronic shut-off may be broken.

So, on the OP's 7 Mag, he will have to determine several measurements, Length of headspace and dia at the web where his bolt will close easily. I am sure that I have already bored the heck out of most reading this so I will go no further into problem-solving at the web dimension, and it is not related to the web.

The very best gunsmiths will take a particular brand of brass, design a reamer around that brand of brass where the Headspace length is minimal, and take into account the Web dimension of that particular brand of brass. You hear a of talk of neck dimension, throat dia dimension, and throat length, but few if any ever speak of the web and shoulder length as solving these two issues that make the phone ring with orders.

I am not a gunsmith but have dealt with these issues for over 30 years with my own reamer designs on wild cats and magnum long range hunting rifles.

 

[Mike Matteson]

"Does headspace off the belt mean there is 1 or 2 thousandths space between front of the belt and chamber belt notch?"

This is correct, and the amounts can vary somewhat up to .005 and can be more. Unless specially ordered by the gunsmith, Head Space gauges for belted mags are always off the belt.

Using a 35 caliber ogive gauge with dial caliper, you can measure the headspace of new unfired brass and then how much it grows after it is fired.

My 7 Rem mags and 300 WM loved an accuracy node right up at the top of the pressure curve, so brass usually lasted 5 firings on Rem brass and more on Winchester.

Lots of BS out there on sizing, but bottom line, you have to size enough of the Web where the bolt closes easily, but not too much. So, using the ogive gauge you can set some standards for a particular chamber

New brass headspace length Fire formed length Tight extraction length Neck sized length with Forster Neck sizer
Minimum and Max in the lot needs full length sizing bump shoulder .002 or more

The other can of worms is web dia, and BS abounds in internet lore on this issue. BS repeated becomes gospel truth. Many of the top gunsmiths in the country design proprietary reamers based on the Web dia, Shoulder dia, shoulder length, neck size, freebore dia, etc.

Today, the most ignorance lies in web dia of the new brand of brass that you are using vs the Reamer dimensions with production dies that vary. Realize that all reamer makers have a +/- tolerance of 0.0005 in their grinding, so you can get a smallish reamer or a slightly over size. Having problems often leads to a chamber cast with cerrosafe vs just ASSUMING that the reamer print is correct.

Many people send in their dummy rounds to the reamer maker and have the reamer maker make a reamer off of those several pieces of brass. The employee of the reamer maker may or may not be aware of the tolerances needed between the web of the case and the reamer for proper extraction, focusing on the neck dia, freebore dia, and freebore length for the dummy round supplied.

Many of the most successful gunsmiths in this country will take new brass, add a minimum of .0034 minimum for a hunting round, and match shooters may run a tighter .0023 over new brass dimensions. Recently in a conversation with two very experienced gunsmiths and National Match shooters told me that they add .005 and as much as 0.010 over new brass dimensions in order to not get Premature pressure signs with its related extraction issues.

I have personally experienced over size NEW brass issues with many of the Lapua cases, Norma cases, and RWS that are larger in the web vs their USA Saami spec counterparts. Peterson, AGD, and Alfa all have their web dimensions often different. So, the advanced reloader has to be aware of their Web dimensions and adapt accordingly.

New brass web dimension fully formed web dimension Max web dimension that needs full-length sizing

There is more than a double barrel butt load of bad information on Web dimensions in Super accurate long-range hunting rifles.

You need a micrometer that measures to 0.0001 to measure web dimensions as any machinist will tell you, never trust dial calipers and I have all the best....trust me on this issue. A $39 I-Gauging micrometer & Shars is well worth the money spent(ebay). I like the mechanical digital as they are harder to make a mistake reading. A reloader does not need a mic that measures to the 0.00001, and I would not advise you to spend money on one of these electronic mics as the first time you drop it, the electronic shut-off may be broken.

So, on the OP's 7 Mag, he will have to determine several measurements, Length of headspace and dia at the web where his bolt will close easily. I am sure that I have already bored the heck out of most reading this so I will go no further into problem-solving at the web dimension, and it is not related to the web.

The very best gunsmiths will take a particular brand of brass, design a reamer around that brand of brass where the Headspace length is minimal, and take into account the Web dimension of that particular brand of brass. You hear a of talk of neck dimension, throat dia dimension, and throat length, but few if any ever speak of the web and shoulder length as solving these two issues that make the phone ring with orders.

I am not a gunsmith but have dealt with these issues for over 30 years with my own reamer designs on wild cats and magnum long range hunting rifles.

Interesting! I'll have to watch and record next time I am out with my belted mag's. One of these days I will get my new 338WM, with a 26" barrel. So it will be brand new. I'll have watch it very closely. The reason I had this rifle built was to achieve 2" more in barrel length to see if I could achieve the same velocity with H4350 powder rather than W-760 powder. My concerns are temp sensitive powder. Nornally I neck size my brass in my belted mag's. Even to the point I don't totally resize the neck.
I looked up Forster neck sizing dies. Only found 7mm Mag die with bushing. If you have another source, please advise. I will spend the money on those dies, and see what I get out of them.

 

[VinceMule]

Mike, Few know that the standard Forster Neck sizers will bump shoulders, and I am not talking about the neck sizers with the bushings!

Merry Christmas!