Signs of case head separation after only 5 firings?

[SWThomas]

I'm using Lapua 30-06 brass and FL sizing it in a bushing die to give me 0.001-0.002 should bump. I'm firing it in a bolt gun. I noticed some abnormal marks on the case and decided to investigate. It was down toward the case head and only on about half of the case. I cut one open and sure enough, the precursor of a case head separation. I found 4 more that showed the same sign and culled them from the group.

Two questions: why am I seeing this after only 5 firings? And should I toss out the rest of the 5X fired cases from this lot?

 

[wolley]

The only 30-06 bras I have ever had show rings from impending separation was Hornady. Everything else had split necks 1st. If you are truly only bumping the shoulder 1 to 2 thousandths then I would suspect something hinky with the brass. Lapua doesn't mean "always perfect".
As far as chunking the whole lot. I wouldn't. Check with a bent wire and cull the ones with deep rings. The ones with barely perceptible rings will go at least one more cycle. Especially in a bolt gun.
Anneal the rest, load em and shoot em.

 

[Chief 101]

my opinion only but case head separation comes from improper headspace. My experience with this is that setting the shoulder back too far allows the stretching that causes head separation. My solution for this would be to find a fired case that causes the bolt to close hard or not at all, then, back off the sizing die and size test fit and tighten the size die slowly until you get the bolt closing where you want it. Personally I like a slight resistance, that way I know the sized case fits tight in the chamber. After fighting this problem 40 years ago this is the solution I came up with that works for me. This is the way I set up sizing dies for all my reloading...hope this makes sense

 

[Savage99]

I agree with Cheif 101 on how to adjust a FL die.

However your rifle's chamber could have excessive headspace itself.

Check it with a no go gage or put tape shims on new brass and measure it.

Also some brands or lots of new brass might have more or less headspace than another. I found that the WW 7mm RM brass had tighter headspace than another brand.

Thus when you reach inside of every case with your feeler rod to check for insipiant separations can throw out the weak cases.

When you set the FL die for that rifle hold back the firing pin with it's safety so you can feel the bolt close on the shoulder.

If your bolt does not have a M70 type safety you can hold back the firing pin by gripping the pin in a vise and putting a coin behind the shroud.

 

[jlow]

I agree with Cheif 101 on how to adjust a FL die.

However your rifle's chamber could have excessive headspace itself.

This is a good point. Always check the headspace of your new brass before and after it has been fired and you will be able to figure out whether the chamber have excessive headspace. Just bumping back slightly afterwards will not help if this is your problem as the damage has already been done.

 

[Preacher]

99% of case head separation is due to improper sizing die set up..

 

[Dgd6mm]

99% of case head separation is due to improper sizing die set up..

Bingo, and this is 100% true.

 

[amlevin]

I'm going to cast my vote for the rifle headspace being excessive.

Have you measured the cases after firing with a case gauge? If so, how far do the case heads stick out of the gauge?

 

[farmerjohn]

Check out your case length. What youfeel bumping when you close the bolt may be the mouth of the case. Ran into this a while back with a 30BR and a 1.510 Robinett reamer. Farmer

 

[Turbulent Turtle]

SWThomas, do you resize your virgin brass before first use or was this once fired factory loaded brass?

 

[Greyfox]

I would want to know how you are determining that you are moving the shoulder back .001-.002"? If you are using a headspace gauge, that is one thing. If you are relying on die adjustment by feel, that can be very deceptive and usually inaccurate.

Rick

 

[Ggmac]

Headspace could be OK . Ive seen more than one barrels installed using headspace gauges , only to find out the barrel was not chambered deep enough . Sometimes the case will blow , others if chambered near correct , will show signs of case seperations. All because of unsupported cases.
Of course this usually only happens on pre-fit barrels using barrel nuts .
I hope This makes some sense

 

[SWThomas]

SWThomas, do you resize your virgin brass before first use or was this once fired factory loaded brass?

For the 30-06 I have only used Lapua brass and All I do it load them and shoot them when they're virgin.

 

[SWThomas]

I would want to know how you are determining that you are moving the shoulder back .001-.002"? If you are using a headspace gauge, that is one thing. If you are relying on die adjustment by feel, that can be very deceptive and usually inaccurate.

Rick

I don't know how else someone would verify they're bumping the shoulders than measuring it.... I've never even heard of someone doing it by feel and then telling people they bumped it back by 0.001...

I use a Sinclair Comparator body with a 30-06 bump gauge insert. I measure the brass after it's initially fired, gain an average, and then set the die to when it bumps the longest one back 0.001-0.002.

 

[SWThomas]

Headspace could be OK . Ive seen more than one barrels installed using headspace gauges , only to find out the barrel was not chambered deep enough . Sometimes the case will blow , others if chambered near correct , will show signs of case seperations. All because of unsupported cases.
Of course this usually only happens on pre-fit barrels using barrel nuts .
I hope This makes some sense

The rifle was built by a very experienced gunsmith. He used a Serengeti reamer that I supplied and chambered it himself with a Bartlein blank. I didn't watch him do it but he used headspace gauges when barreling/chambering this rifle. I would lean more towards me doing something wrong or the brass being bad before I would blame him for shotty work.

 

[Ggmac]

I agree , this usually happens when prefit barrels are chambered to shallow , then installed using gauges , but leaving a longer than safe case unsupported.
Gary .

 

[BoydAllen]

With a long case, a dry chamber and loaded round, and a relatively mild load, you can run into a problem....if you are bumping from the measurement of fired brass, that has had its primer removed, or seated deeper. Let me explain. The 30-06 has a relatively small shoulder angle, and that, combined with the usual clearance of new brass, and the force of the striker assembly, and push of the exploding primer against the bottom of the primer pocket, will drive the case farther forward in the chamber than when it was loaded, then, if the load is middle of the book, and the lack of lubrication, body length, and chamber finish afford excellent traction as the pressure comes up from the powder burning, the case may not fully stretch to firm contact with the bolt face. If you put the fired case between the jaws of a dial caliper, with a jaw across the primer, you may be able to see a gap between the case head and the caliper jaw (when you hold it so that there is a light source behind it) that indicates that the primer is protruding very slightly. (Before you do this, carefully file any crater flush with the primer.) If you then use that case as a reference to set shoulder bump, you will have too much total case "headspace" or has some have called it gap space, and if you repeat the process several times, you will get just what you have described. May I suggest that you neck size and fire a case with loads that are as hot as you can safely fire in your rifle (after carefully approaching that charge from below, weighing all charges), until the case is tight as you close the bolt, and the datum to head measurement (taken with reseated or removed fired primer) stabilizes at its maximum value. You can then mark and set this case aside as a reference, for setting shoulder bump for that rifle. (The brand of the case does not matter.) I believe that this should solve your problem. Generally, if I can easily chamber a deprimed fired case with acceptable bolt closing feel, I set my FL die for zero bump, as compared with the fired case, but I prefer to use a reference case, because that is more precise. Be aware that factory brass varies in hardness (even Lapua) and for that reason, a given die setting may not produce the same amount of shoulder bump. Differing amounts of lubrication, and times at the top of the ram stroke will also produce differences in bump. I will leave that for another time, since achieving uniform bump is an article of its own.

 

[bigedp51]

SWThomas

Take a new unfired case and measure its overall length and write it down, then just using your fingers start a fired spent primer into the primer pocket. Now chamber this test case and slowly close the bolt letting the bolt face seat the primer and then remove the case. Now remeasure the cases overall length again and write it down and subtract your first case measurement from the second, and this will be your head clearance.

Your head clearance is the amount the case will have to stretch to meet the bolt face when fired pictured below.

Your problem as described is very common when reloading for milsurp rifles with longer headspace settings "OR" new brass with "SHORT" cartridge headspace. Meaning how far the brass has to stretch on the first firing and starts the brass thinning in the base web area.

Below I use the RCBS case mastering gauge to check for thinning in the base web area which is far more accurate than a bent paper clip.

And a Hornady cartridge case headspace gauge is a great tool for measuring your fired and resized cases for proper shoulder bump.

Below is a "ball park" idea how long cases will last when full length resized with the die making hard contact with the shell holder (cam over) on a new Savage .308 rifle. I said "ball park" because this article did not give the rifles headspace setting or how much the shoulder was bumped back during sizing.

In a nutshell what shortens case life is how far the case stretches on the first firing and the amount of shoulder setback when resizing.

The above message was brought to you by “The Society for the Prevention of Cruelty to Lapua Brass”.

 

[Greyfox]

I would want to know how you are determining that you are moving the shoulder back .001-.002"? If you are using a headspace gauge, that is one thing. If you are relying on die adjustment by feel, that can be very deceptive and usually inaccurate.

Rick

I don't know how else someone would verify they're bumping the shoulders than measuring it.... I've never even heard of someone doing it by feel and then telling people they bumped it back by 0.001...

I use a Sinclair Comparator body with a 30-06 bump gauge insert. I measure the brass after it's initially fired, gain an average, and then set the die to when it bumps the longest one back 0.001-0.002.

Sir,
I don't know you at all and from reading this and other forums I see that people do all kinds of things that sound ridiculous including holding brass in their fingers and thinking they are heating a case to 750º to anneal it. I also know that there are shooters who size their brass strictly by the feel of their bolt closing and think they are doing "about .001".

Now that I know enough about you, I will not bother you with silly answers and questions on future threads. Matter of fact, it looks like you already know most everything anyway and I wonder why you bother to ask.

Rick

 

[Dgd6mm]

biged, were those cases FL sized before the 1st firing? Sorry SW, I just had to ask, did not mean to get off the subject.