Case head separation due to FL resizing brass?

[Vol1975]

so. This has happened twice now and tell me what you guys or gals think.

First about 10 years ago I FL resized some Remington brass (7mm mag) and when I reshot this brass I had several case head brass spilts right above the belt. Luckily was able to extract from gun. I stoped what I was doing and basically threw the brass out. I chalked it up to older brass and when I resized the brass I stressed the brass by FL resizing it back down to Sammy specs.
For a long time I never had a problem again but I didn't use the FL dye a lot either. Mostly shot a 06 with lower pressure and a ton of new brass. Anyway...

So fast forward to this weekend.
Hornady brass and 7mm again. Now this brass has had about 3-4 firings when I had a total case head separation. Again luckily I screwed up a dye instead of a gun. Anyway. Brass stuck in dye when I was bumping shoulders back .001 th.
Where it failed was right above the belt. Lube was plenty and the amount I reduce next to the belt was approximately .002-.003. I will admit I run top speed and pressure on this round so this could be a factor.
So my question is 2 folds. Is their a cut off limit that one follows on the amount of brass is shot. And 2 does the FL resizing dye that one uses stress the brass enough to promote failure in this manner.
Anyway Im pretty careful on measurements and how much I'm bumping stuff back. so this has happened twice now has gave me concern on using older brass and FL dyes in these magnums.
Closing. Trashed all older brass at this point and backing off a grain on my load.

Any thoughts?

 

[sedancowboy]

There at least a 100 threads dealing with this issue so try using the search engine above. However I will try and answer your questions briefly. There are several things that could be going on. High pressure being one I can't help you with that one but to say just back off a bit. How are you determining your shoulder set back? Do you have a bump gauge? If you are actually only bumping the shoulders back .002 and not running over pressure loads then there is no reason to have case head separation on a belted case. In fact you should be headspacing off the shoulder and the belt is not in play at that time. Perhaps the brass has been shoot in another rifle? Usually if you start with new brass the shoulder will grow about .010-.018 on the first firing because it is headspacing off the belt. Perhaps it is not fully blown out and so while you think you are only bumping your shoulders back .002 you are in fact bumping them back much more. How often are you having to trim your brass and how much? Are you annealing? The simple answer is you are overworking your brass and you will have to determine what is causing it. The brass is stretching out a little on each firing until it fails in front of the belt.
Hope that help
Henry

 

[crystalgayleguy]

what brand of brass it could be in that one piece of brass just weak when it was made

 

[nmbarta]

Your hot loads aren't helping obviously, how are your primer pockets after 3-4 firings.
I had some problems with case head separation with hornaday 7rm brass, switched to nosler and haven't had a problem.

 

[SilverbulletMAG]

I have the same problem with Hornady brass in 338 Win. It seems to be pretty thin brass.

 

[BallisticsGuy]

Belted mags, gotta love em to hate em properly. They come with their own unique problems because of the belt.

My strategy is simple, don't let the belt screw me up. So don't bump shoulders unless you have to to get the bolt to close. That sets you up so it headspaces on the shoulder instead of the belt. Then, don't full length size unless you have to. You'll get better brass life from not working the brass so hard, especially with regard to CHS.

For me this means setting the rifle up for zero headspace to begin using a pack of new brass as a gauge instead of a proper go gauge. This makes me toss about 10% of a lot of new brass that will not fit because of belt thickness variations. Then neck sizing only as long as I can rounds things out. Pushing a belted magnum is just going to hurt brass life, period. Pressures climb, brass flows. That's how that bakes out. If you want brass life, step 1 is to stop pushing things so hard. Step 2 is stop working the brass so hard. Do the things you need to do and no more things than that when reloading.

 

[Vol1975]

Belted mags, gotta love em to hate em properly. They come with their own unique problems because of the belt.

My strategy is simple, don't let the belt screw me up. So don't bump shoulders unless you have to to get the bolt to close. That sets you up so it headspaces on the shoulder instead of the belt. Then, don't full length size unless you have to. You'll get better brass life from not working the brass so hard, especially with regard to CHS.

For me this means setting the rifle up for zero headspace to begin using a pack of new brass as a gauge instead of a proper go gauge. This makes me toss about 10% of a lot of new brass that will not fit because of belt thickness variations. Then neck sizing only as long as I can rounds things out. Pushing a belted magnum is just going to hurt brass life, period. Pressures climb, brass flows. That's how that bakes out. If you want brass life, step 1 is to stop pushing things so hard. Step 2 is stop working the brass so hard. Do the things you need to do and no more things than that when reloading.

10/4.
I typically in the past only neck size my brass along with only bumping the shoulder back .002ths. Measure with proper tool to give me the free area of .002. That Measurement of .002th from fire formed from the shoulders. I typically don't run max pressure but this is maybe close. The primers are just flatting out but I have no ejector marks. 175 gr pushing 2925fps for those curious. My main goal is to just reduce the brass around the shoulders and maybe around the belt to load comfortably.

As far as stressing the brass that was what I was getting at on the original start of this thread. My problem that I've found in 29 years reloading is when I take a belted magnum and FL re-size it to any amount on brass. Brass that has been shot more than a few time (say at least 4 shots) is when I've experienced splitting of the brass above the belt. This reduction on the area right about the belt seems to me the weak link on stressing the brass in any form. With that being said it's only happened a small hand full of times on 1000s of rounds down range. My reduction around the belt from fire formed to resized is approx .003 ths measured.

In the end I'm going to back off the current load and not stress the brass with a FL dye. I didn't think by moving the brass .003 th above the belt would make that much of a difference but it did.

 

[cape cove]

I have 5 belted mags and I find that if I set my FL die to headspace the case when sized off the shoulder rather than the belt and set it to bump the shoulder .002-.003 I get as good case life as any other non belted case. JME

 

[CaptnC]

I started one of the 100 threads on the subject...I have 2....7mm RM, one a custom based on a old Mauser action and one Factory Weatherby.

The Weatherby doesn't have any issue with brass life, but the mauser will eat a case in half just above the belt after three firings.

I had the smith triple check the head space, but is still eats brass. It's been in the safe for a long long time because its so aggravating.

I even quite shooting the Weatherby...been at least 15 years since I've shot either one!

 

[BountyHunter]

I started one of the 100 threads on the subject...I have 2....7mm RM, one a custom based on a old Mauser action and one Factory Weatherby.

The Weatherby doesn't have any issue with brass life, but the mauser will eat a case in half just above the belt after three firings.

I had the smith triple check the head space, but is still eats brass. It's been in the safe for a long long time because its so aggravating.

I even quite shooting the Weatherby...been at least 15 years since I've shot either one!

The problem is excess shoulder pushback not FL sizing. Plus it you are using the same dies and adjustments for both guns you need a set of skip ottos die shims to adjust the variance in shoulder pushback needed without having to change fixed die adjustments. The rifles have different headspace. Forget belts, cam over etc and adjust dies for .002.
Measure shoulder headspace on both rifles fired brass. Adjust the die to to bump shoulder .002 on the shortest brass and lock die. Now for longer headspace, forget going for cam over, adjust for the.002 shoulder bump using shims. Start with die about 1/8 above shell holder and oy work it down until you get the .002 shoulder bump. On longer brass start with the shim for amount of difference between the 2 head spaces. slowly work down. USe die shims under die to adjust shoulder to .002 on that brass.

 

[trhall]

so. This has happened twice now and tell me what you guys or gals think.

First about 10 years ago I FL resized some Remington brass (7mm mag) and when I reshot this brass I had several case head brass spilts right above the belt. Luckily was able to extract from gun. I stoped what I was doing and basically threw the brass out. I chalked it up to older brass and when I resized the brass I stressed the brass by FL resizing it back down to Sammy specs.
For a long time I never had a problem again but I didn't use the FL dye a lot either. Mostly shot a 06 with lower pressure and a ton of new brass. Anyway...

So fast forward to this weekend.
Hornady brass and 7mm again. Now this brass has had about 3-4 firings when I had a total case head separation. Again luckily I screwed up a dye instead of a gun. Anyway. Brass stuck in dye when I was bumping shoulders back .001 th.
Where it failed was right above the belt. Lube was plenty and the amount I reduce next to the belt was approximately .002-.003. I will admit I run top speed and pressure on this round so this could be a factor.
So my question is 2 folds. Is their a cut off limit that one follows on the amount of brass is shot. And 2 does the FL resizing dye that one uses stress the brass enough to promote failure in this manner.
Anyway Im pretty careful on measurements and how much I'm bumping stuff back. so this has happened twice now has gave me concern on using older brass and FL dyes in these magnums.

2 tools that anyone reloading a belted magnum should have. A digital Head Space Gauge and Belted Magnum Collet Resizing Die. Both available from Larry Willis. Using both of these will prolong the life of your brass period.
http://www.larrywillis.com/
Closing. Trashed all older brass at this point and backing off a grain on my load.

Any thoughts?

 

[WV338]

I had the same problem until I bought a Belted Magnum Collet Resizing Die from Reloading Technologies.

 

[BallisticsGuy]

Pushing the shoulder back is a big part of the problem. If you can close the bolt, don't bump. If you do bump then bump as little as possible to allow easy enough bolt close to get you happy. Working metal hardens it. Hard metal cracks when worked more.

 

[fiftybmg]

What was the case length after sizing, and did you trim before reloading ?