case head separation

[rfair]

My shooting buddy and I were shooting yesterday and I'd like to talk to you about the last 3 cartridges he fired! The first one had 2/3 rds of a ring around it, the second one had a ring all the way around it, and the third one would not extract. We dropped a cleaning rod down it and the case head popped off clean! now my question to you is why didn't some of the other cases that had been presumably been reloaded the same amount of times fail? Could there be a problem with the chamber?
His powder charges are well below max and a load he's been using for quite a while.
Thanks for any input!!!

 

[markr]

Your shooting buddy needs to have the headspace checked on his rifle. If all is well there, he needs to determine if he may be creating excessive hedspace with his reloading tecniques i.e. resizing the brass too much by pushing the shoulder back too far. A lot of people just run the resizing die down till it touches the shellholder and thinks that is good. Depending on his dies and shellholder, this may resize way too much,
Mark

 

[fdshuster]

As markr said, get the headspace checked with go, no-go, and even field gauges. Bolt should close normally on "go", a tight closing on a "no-go" is thought by some to be acceptable, but closing on a "field" is a big no-no. I personally know of a new, unfired factory rifle (shall remain nameless) that was delivered to the customer with a headspace that would esily permit the bolt to be closed on a field gauge. Case head of the first factory round fired (35 Whelen), was blown off with the forward case section remaining in the chamber. The "advice" on the loading die box about screwing the die down 'til it touches the top of the shellholder is the dumbest out there. Get the Hornady or Sinclair o.a.l. gauges and learn what the real dimension is, not some one-size-fits-all. Also a good reason to clean your brass before reloading, and give them a quick look see in the area of the case head looking for the beginning of the seperation ring.

 

[brxbrad]

I've been having the same problem with my new brx. Research in this subject has lead me to believe case head separation can be caused by a few things....Condition of your Brass, Condition of your chamber, too heavy of a load, or improper head space. I'm still in the process of ruling out the cause in my gun. The processes I am following are:
Check ALL your brass for any telltale signs of pressure or fatique. Check your gun for proper head space. Recheck your loading setup ie., If full length resizing is done, Is your sizing die set incorrectly? Here is a link with pics to show you what to look for with your brass. http://images.google.com/images?um=1&hl=en&tbs=isch:1&q=case+head+separation&sa=N&start=21&ndsp=21
A good way to check the inside of your cases is to use a sharpened paper clip. The paper clip is then used as a “feeler gauge” to check the interior case walls. Insert the bent end of the paper clip into the case mouth, and drag the sharpened point along the interior case walls. Any thinning or cracking can be readily felt as the point dips across the damaged area. Check all your brass. Any questionable cases should be tossed. When case head separation occurs, the bolt in your gun gets excess pressure and can lead to faliure or injury.
I also found a video on youtube made by Ammosmith.com on how to estimate maximum pressure http://www.youtube.com/watch?v=SUPl4fnBJ8o&NR=1 In my case, I full length size my brass when I really only need to neck size. I think my die was set wrong and ended up bumping the shoulder back to far casing improper head space. I'll be going back to the range this week to comfirm. Here is another link from Varmital and shows how pressure is distributed through a bottle neck case. Watch the animation. http://www.varmintal.com/a243z.htm. I sure I've left alot out, but maybe this will help. My gun is new and I'm still working out the bugs but if you've never experienced this problem before, with this paticular gun, I would suspect the brass or the load. Hope this helps......

 

[rfair]

Thanks guys for the input! I don't think the head space should be a problem because the factory rifle he's shooting has been shot for years. I do know he's a good reloader because he helped me set my fl die up to bump the shoulder just .002. I guess his die could have moved a bit.
maybe he'll chime in after a bit, I told him to watch this post! I put it on here because I wanted to know as well!

 

[Preacher]

99% of the time case head separation is caused by improper headspace from a die not set up right for a particular chamber..... If the case goes into the chamber with no pressure applied to the bolt, when it has the firing pin assembly out of it, you will have a headspace problem however small it might be.... if it's not corrected you will have separation problems.... Just like bending a coat hanger back and forth repeatedly, sooner or later it will break from the stress...............

 

[BoydAllen]

One more thing....because brass work hardens from being repeatedly fired and FL sized, and work hardened brass has more spring back, requiring the die to be set closer to the shell holder, a die setting that is right for a work hardened case will move the shoulder of a once fired case farther than is desired. If your friend did not know this, and used an old piece of brass to set his die, and then used that setting to bump back fresh brass, he is getting more bump than he planned on.

 

[rfair]

Thank you preacher and Boyd Allen!

BoydAllen said:

{ If your friend did not know this, and used an old piece of brass to set his die, and then used that setting to bump back fresh brass, he is getting more bump than he planned on.}


I do know he has just 1 308 so all the brass he has would have been shot through it so wouldn't a fresh pc of brass be shorter from the shoulder to the bottom before being fireformed and wouldn't the die set up for the fired rd { to bump it back .002 } not mess up a new case?
I also read the other post on case head separation and saw your response! Good idea with the paper clip!
Thanks again!!

 

[BoydAllen]

When I wrote "fresh" I meant a fired case with only a few reloadings on it. If you are loading new brass, all that a FL die would do is to possibly straighten the neck. It wouldn't touch the shoulder, or size the body.

 

[shootsanything]

One more area where I got myself into trouble - I did not notice my FL sized brass had stretched and this was causing the seating die to try to crimp on a bullet with no crimp ring. Long story short the cases ended up with the shoulder moved back during bullet seating because of the die trying to crimp. Too much headspace and too high a pressure and you can guess what happened. Took me a while to find though - the Stoney Point tool said they were fine after resizing - I just got lucky and looked at loaded bullets to find the issue.

I check case length more regularly (like every reloading) now.

 

[Innovative]

rfair .........

The odds of having a factory rifle made with incorrect headspace is one in a million.

It's far more important to measure your handloads (at the shoulder), and compare it to one of your fired cases. Then you'll see the difference, and that will help adjust your die height correctly. If you maintain -.001" to -.002" clearance at the shoulder - you'll never see another headspace separation.

Take a look at www.larrywillis.com and you can see the tool I recommend.

- Innovative

 

[rfair]

Thanks again for any info you guys!

Inovative,
That digital head space gauge looks handy! I'll have to get one of them a little later!

 

[fdshuster]

Larry/Innovative: The 35 Whelen must have been the "one-in-a-million". I was 10 feet away from the guy (a friend) when it happened. He took the rifle to a local 'smith who used his little finger to demonstrate how easy it was to close the bolt on a field gauge. It was sent back to the factory, with the original factory loads including the ruptured ( same maker/ rifle & ammo) case. Three months later it was returned with a note saying they could find nothing wrong with the rifle. It was then taken back to the same 'smith who closed the bolt normally on a go-gauge, but could not close it on a no-go. The rifle was trouble-free thereafter. No, I did not believe this was the problem with the rifle in question, just used it as an example of how excess headspace can cause case head failure.

 

[Innovative]

fdshuster ........

Defective factory loads are another "one in a million" - but it happens. However, for a rifle case to split the brass, it needs to be very hard and extra thin above the web. It also needs to have a bit of clearance (at the shoulder) for the case to stretch. If those conditions are met and you're on the high side of normal SAAMI spec tolerance ...... that would be enough.

There should be -.001" or .002" clearance at the shoulder for quality handloads, but no more than that. Measuring your handloads (compared to your chamber) is the best way to know "exactly" how they fit in your particular rifle.

- Innovative

 

[fdshuster]

Larry@ Innovative: Yes, agree to all of the above, but in this instance the rifle had to have left the factory with radically excessive headspace, or the bolt would have never easily closed on a field gauge. And, as I said " get the Hornady or Sinclair o.a.l. gauge and learn what the real dimension is", a practice I've always followed, for many years now. I personally have never had a complete case head seperation. On rare occasions see the start of the seperation ring, from normal usage, and the case is immediatley relagated to the scrap container.