Case head separation

[moe africa]

Good Day all
I've recently found a few of my lapua palma cases with signs of case head separation,
The brass has been fired 7 times, 2 times in 1 rifle ,5 in the current barrel and generally the load was 44gr of n150 with a 175gr running at 2730 from a 28" barrel
Most people have mentioned excessive headspace, I've measured numerous times with a whidden case gauge and the bump was between 2.5 and 3 thou almost always
Could there be any other causes ?

 

[Tim Singleton]

The only other thing I know of that can cause this aside from excessive re sizing is
Unsupported case head

 

[jwv2001]

Good Day all
Most people have mentioned excessive headspace, I've measured numerous times with a whidden case gauge and the bump was between 2.5 and 3 thou almost always
Could there be any other causes ?

Are you saying the "bump" was moving the shoulder after every firing? In that case, then yes, that's the problem, You are moving a fireformed case up to .003" shorter than the chamber. Maybe you should think about backing off the sizing die to mirror the chamber dimension and only size the neck.

 

[moe africa]

The only other thing I know of that can cause this aside from excessive re sizing is
Unsupported case head

Just some pics for reference

 

[Tim Singleton]

how often are you having to trim the over all length?

 

[moe africa]

how often are you having to trim the over all length?

I've trimmed at 6 firings it was at 2.025" , yet a borescope picture revealed there was still space to grow
The picture is at 2.025"

 

[BoydAllen]

Have you done the paper clip trick and felt a groove inside of those cases?

 

[Straightshooter1]

Good Day all
I've recently found a few of my lapua palma cases with signs of case head separation,
The brass has been fired 7 times, 2 times in 1 rifle ,5 in the current barrel and generally the load was 44gr of n150 with a 175gr running at 2730 from a 28" barrel
Most people have mentioned excessive headspace, I've measured numerous times with a whidden case gauge and the bump was between 2.5 and 3 thou almost always
Could there be any other causes ?

IMHO, I think repeated sizing with bumping that much can easily do that. . . especially if the die is sizing a lot down near the web.

The only other thing I know of that can cause this aside from excessive re sizing is
Unsupported case head

If not that, then this ^^^^^

 

[NorCalMikie]

Bumping the shoulder TOO MUCH will do that!! If the fired case will re chamber with no resistance, neck size, prime, load and go shooting.

 

[HandgunHTR]

Have you done the paper clip trick and felt a groove inside of those cases?

This.

Also, did the line just show up?

 

[D-4297]

I anneal , re-size ( Bump ) after every firing , but my Die is set to only Bump the case .001 and I currently have over forty reloads on my practice cases . My Barrel has been engraved 2.614 when my "Smith" cut the Barrels , and my cases get "Bumped" to 2.613", read off of my comparator / Calipers . I check for trim every firing , and usually only have to trim about every fifth or sixth firing , and that is to keep them uniform , within .003 total length .
The load is 43.7 gr. of N-150 . Bullet is 200 gr Berger Hybrid Target with a Rem 7-1/2 primer . We are running a comparable load , and I'm running a heavier bullet at 2665 - 2670 FPS !
As others have said , you may be over Bumping your cases .
The other question I have ; since you didn't mention it was : Do you anneal after firing ?

 

[moe africa]

This.

Also, did the line just show up?

I do feel a groove ,with paperclip
Yup it just showed up

 

[moe africa]

I anneal , re-size ( Bump ) after every firing , but my Die is set to only Bump the case .001 and I currently have over forty reloads on my practice cases . My Barrel has been engraved 2.614 when my "Smith" cut the Barrels , and my cases get "Bumped" to 2.613", read off of my comparator / Calipers . I check for trim every firing , and usually only have to trim about every fifth or sixth firing , and that is to keep them uniform , within .003 total length .
The load is 43.7 gr. of N-150 . Bullet is 200 gr Berger Hybrid Target with a Rem 7-1/2 primer . We are running a comparable load , and I'm running a heavier bullet at 2665 - 2670 FPS !
As others have said , you may be over Bumping your cases .
The other question I have ; since you didn't mention it was : Do you anneal after firing ?

I've annealed at 3 firings

 

[Bill Norris]

Consistently moving the shoulders back .003 will eventually cause the case head separation.

 

[Webster]

Good Day all
I've recently found a few of my lapua palma cases with signs of case head separation,
The brass has been fired 7 times, 2 times in 1 rifle ,5 in the current barrel and generally the load was 44gr of n150 with a 175gr running at 2730 from a 28" barrel
Most people have mentioned excessive headspace, I've measured numerous times with a whidden case gauge and the bump was between 2.5 and 3 thou almost always
Could there be any other causes ?

If you can rechamber a fired case easily you should not be bumping from this dimension. Size with no bump until the case is tight or maybe 2-3 firings with no bump to get your bump from dimension. Don't know about case gauges (+/- 0.002" machining tolerance?) . I'm sure it's made to some std SAAMI dimension and not your actual chamber.

 

[Jason D Hostetter]

What action? .0025-.003" is more than my liking, of .001-.0015", but shouldn't cause that after 7 firings on palma brass, with what I consider a creampuff load.

 

[C.E.Smith043]

Good Day all
I've recently found a few of my lapua palma cases with signs of case head separation,
The brass has been fired 7 times, 2 times in 1 rifle ,5 in the current barrel and generally the load was 44gr of n150 with a 175gr running at 2730 from a 28" barrel
Most people have mentioned excessive headspace, I've measured numerous times with a whidden case gauge and the bump was between 2.5 and 3 thou almost always
Could there be any other causes ?

I once had an issue with an rcbs die in my 243. It was squeezing the base area a little too much and causing early case head separation.

I sent the die in and they sent me a new one, problem solved

Your best bet is to send in a few fired cases and have a custom die made.

 

[Jason D Hostetter]

The reason I ask, is I've seen people put a 20 or 30 degree breech entry barrel on a flush bolt action or vise versa and have too much gap, but the correct headspace. It can happen with any setup, but happens more often when the bolt doesn't match the breech. It looks like not enough base support, either way.

 

[M-61]

I've measured numerous times with a whidden case gauge and the bump was between 2.5 and 3 thou almost always

Why? Why that amount? What purpose?
So push the shoulder back ‘almost always’
3 thousandths. Then fire it . Where did you think that ‘3 thou’was coming from? How many times could you that brass? Guess the paper clip trick is giving you a real good idea. 7 times…. well you’re well on your way to the case separation.
I have to ask my first question again. Why did you feel the need to push the shoulder back at all never mind 3 thousandths?
You must have a clear understanding of what the case is doing when you pull the trigger. Find a mentor to explain this. The paper clip trick and annealing is a waste of time and does not address your problem.