Case head separation?

[Daryl S]

Certainly is a "belted magnum ctg".

 

[Rafiki]

Certainly is a "belted magnum ctg".

Really, that one image looks like a rimmed cartridge. Where's the belt? Looks like it has a prominent rim. How could that happen. Wouldn't the chamber constrain the stretching in that area? Makes no difference since clearly there's a problem here.

Oh, I know what happened. I was going through the images of the post from the thumb nails and the image I was referencing is actually from another post. My bad

 

[Daryl S]

Pull the bullets, throw away the powder and brass.

Cases stretch just above the case head in a straight line perpendicular to the case. See the stretch ring flanked by blue lines,

View attachment 783085

Whatever happened to your cases I don't know but I bet the brass itself has defects. I've never seen any brass like that!

This picture with the dial indicator is of a rimmed case. ALL of the others show belted magnum cases.

 

[Daryl S]

Definitely not a "normal" case head séparation caused generally by excessive headspace, either due to chamber dimensions , or caused by pushing the shoulder back when sizing the cases. With sizing the culprit, this usually takes more than 2 re-sizings.

 

[Mark A Ouellette]

@Rafiki I posted a photo in my library of a near case head seperation on a 500-416 case.
Cases ready to seperate be they rimmed, rimless, or belted rimless all form a visable line.
When measured, the brass is noticably thinner under the line.
One or two more shots and a case extractor is required...

 

[Mark A Ouellette]

Ah, what cartridge is this? Certainly not a belted magnum as in the other images.

Certainly is a "belted magnum ctg".

Since I am not the OP, I may not have a photo handy of a near case head seperation on a belted case.

@Daryl S , Clearly @Rafiki was refering to the photo of the 500-416 rimmed case of which I posted a photo of since he quoted my post.

Here's some eye candy for technical folks,

Craighton Audette concentricity and wall thickness gage (no longer available),

Currently available NECO concentricity and wall thickness gage,

Anvils I fashioned for the above gages from1/4" stainless rods I bought on Amazon.
The longer anvils are required for long cases.

 

[Daryl S]

Yes, I understand the error. Tks.
Many belted magnums have had normal case head separations due to excessive headspace for the round, caused by having a short bodied FL die, while having a longer bodied chamber. I have heard of some guys with .300 Win. Mags. getting case head separations with their 3rd. reload. This is due to touching the die body against the shell holder when sizing in a short bodied die, causing the shoulder to be pushed back excessively. When the case is fired, the body stretches at the web so the case shoulder can push agsinst the chamber shouder. People think the belt prevents problems. NOT! This happens mostly with RCBS dies it seems. That might be because they were the most popular for many years, however it does happen. The only.people whom I have EVER heard of who had to "bump" a shoulder, were bench-rest shooters. At most, the "bumped" a shoulder by a thousandths or maybe 1 1/2 thousandths. This was needed due to their usually maximum pressure loads.
I've not needed to "bump" a shoulder - ever. I partially FL size in those FL dies, but prefer to only neck size. My ammo is checked for cycling.

 

[Huvius]

I had the same problem with a batch of HWS 425WR brass - cracking circumferentially in front of the rim.
That, I’m sure, is because they were made from the same basic cases as their 404 Jeffery brass and the cut for the rebated rim was too deep thinning out the base wall.
This is different in that the cut isn’t as deep as in a 425.
Section the one that didn’t fire and see what’s up in that area.

As an aside, I had a couple boxes of Wolfgang Romey 375 Flanged Magnum that actually cracked and had bubbles fizzing out of the cracks!
No idea what powder they used but that was the weirdest ammo related occurrence I’ve experienced!
Never touched that brand again!

 

[Daryl S]

I've not heard of failures of that sort before. Thanks for posting this Huvius.

 

[fourfive8]

A thought. If you have an example of new brass of a brand that works and an example of the new PPU brass that seems to have a problem… measure the diameters at the belt and the diameters just forward of the belt. Compare

 

[Daryl S]

The holing and burnouts do not appear as a dimension/expansion problem, but as a hardening/hardness problem, in my opinion, of course.

 

[Vintageguy]

Your description of the sound of a muzzleloader with slow ignition is the round doing exactly that. The primer pops but there’s a delay of the charge going off. The primer pop can move the bullet forward to meet the rifling then the main Charge ignites. This is dangerous because it can behave as though it has a bore obstruction causing excessive pressure. It is not an uncommon thing with old surplus military ammo. There’s nothing wrong with your rifle it’s the rounds. Hence the one that wouldn’t fire at all. Why these did this is pure speculation but what they did from your description isn’t in my opinion.

 

[Daryl S]

That is called a hang-fire. VERY bad in.modern guns. It isn't good with flint-locks, either as it is disturbing to the aim.
A cap-lock, rifle, smooth rifle, or pellter (pelletshooter) seems to give as quick ignition as any modern gun. The lead on birds, for instance is identical. With a flintlock, additional lead is necessary.
Many flintlock have seemingly almost as fast ignition as cappers-almost.