260 Rem Brass Issues

[BearNaked]

So i am having partial case head separation when I'm pushing some of the powders on the high end but it is not showing any other pressure signs on any of the charges. So my question is do I just chunk the brass and start new because the brass is shot up or do I take that as a pressure sign and back down? no flattened primers, no heavy bolt lift, no ejector swipes.

I'm running a Savage 260 Remington with a 26" Shillen Barrel.
Brass: once fired 308 military brass, annealed, necks turned to .015", maybe 5 firings on these
Bullet: 130 Berger Hunting VLD
Powder: H4350

Here are my numbers from this weekend.

2 Cases split at 44 grs.

 

[GhengisAhn175]

First A case head separation is a permanent loss of that piece of brass. Period. No coming back to it.

Second, are you sure it’s once fired? Case head separation is unusual at once or second fired unless something was seriously hot but you’re not mentioning popped primers, swipes, ejc. Marks

Third, are you sure it’s even case head separation? Physical signs would be more than just a ring near the case head. You can feel it on the outside and inside (with paperclip or dental pick)

If you think you do have it, lock up that piece of brass on a vise with the case head facing up. Take some pliers to it, lock down and try to bend and rip the case head off. If it comes off cleanly/easily by the ring then I’d say the rest of the brass is compromised if they came from the same source.

***edit: just re read and saw that you’re running a 260 Remington using 308 brass; on top of verifying once fired, how much did you bump the shoulder back? Did you anneal prior to?

Not sure how you formed 308:260 but if you went straight into a 260 Rem die it should be after proper annealing and absolute minimum sizing

 

[BearNaked]

Its case head separation for sure. I have holes with burn marks about a 1/2 inch up from the base. I didn't have any flattened primers, ejector marks, heavy bolt, nothing. just the split around the case head. What is weird is that on the rounds that split, it pushed the bullets about 80fps faster than the previous ones.

I am pretty sure its once fired military brass as I the primers are crimped in and I have to remove that before I can seat a primer. I have about 5-6 reloads on this brass but I thought I would get more reloads out of it before it did this.

I neck down the brass from surplus 308 military brass. I anneal the brass, run it through a small base die, then do a full length die to neck it down, then trim the necks to 0.015" neck thickness, then full length again to get the proper neck tension, and finally I can seat the primer, etc.

I did notice last night I was bumping the shoulders back about 0.010" instead of 0.002" that I did with my 308 before re-chambering it. so maybe that extra stretch every time made the body weak around the case head?

I am running a new batch of the same military brass now. testing my theory of bumping the shoulders back too much as a cause.

 

[PinesAndProjectiles]

Bumping your shoulders back that far was causing your head space to be less than what it should be, which means your brass is stretching .010' every firing. Get some new brass, measure it after firing it, and bump your shoulders .002".

 

[GhengisAhn175]

Oversizing on hot loads will cost case of separation is easy I think you found your answer

If you find your other case like that I would probably either scrap them and start over and chalk it up as a lesson learned or monitor them very carefully

And a future you just need to make sure you’re not bumping back that much

 

[GhengisAhn175]

If you happen to have any access to x-ray equipment you could just take a quick scan of all your cases to see if any have signs of case had separation internally

 

[308pirate]

I did notice last night I was bumping the shoulders back about 0.010" instead of 0.002"

You found your root cause.

100% check resized brass for length between case head and headspace datum and compare to fired brass. Any difference > .002 - .003 goes in the trash.

 

[BearNaked]

well lesson learned for sure. I've been so focused on everything else I forgot about bumping the shoulders back properly. I checked last night because it finally hit that I haven't checked the shoulders.