357 Case Head Separation

[DsGrouse]

Just checked a few of my hand loads and they have the same ring. I use a Lee carbide dies and I never noticed it before. Thanks.

I never understood what caused it. I watched a vid by mighty armory, and he outlined why it happens. I talked to a buddy in ct who says, it's why he sizes with steel dies and lube.

I plan on trying one of these in the near future.

https://www.mightyarmory.com/collection ... -decap-die

[Mags]

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I sized a couple. There are four new unfired Starline cases and four fired Starline cases.

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I am betting there is some work hardening happening with the brass at that spot. When fired, it seperates.
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From the somewhat looking burnt brass, like 5shot, I have to wonder if CFE goes from mild to wild quickly.

[DsGrouse]

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I sized a couple. There are four new unfired Starline cases and four fired Starline cases.

...
I am betting there is some work hardening happening with the brass at that spot. When fired, it seperates.
....

From the somewhat looking burnt brass, like 5shot, I have to wonder if CFE goes from mild to wild quickly.

If you are referring to the quoted picture, shot, five is the new brass. My brass not his. I used a light so as to highlight the line caused by sizing.
1,4,5,8 are new unfired starline brass, 2,3, 6,7 are fired starline brass.

As for his load, I ran a few numbers using GRT, and included a couple of miss drops over his stated 7.3 grains.

7.7 grains is a jump to 20,473 psi. 1365fps
8.0 grains is 22,180 psi 1397 fps
9 Grains is 28,463 psi. 1499 fps
10 grains is 35,737 psi. 1595 fps

Grt says 10 grains of cfep is almost into the -15% Pmax for 357 mag.

I should add that GRT says the estimaged velocity of his 7.3grains of CFE-P is 1320 fps with a PSI of 18,320.

Given his velocity was 1319, I'd say the model is pretty spot on.

[azdover]

CRAP!!! I was using Power Pistol not CFE-P. Sorry about the error. I had it written down right there in my notes in front of me and still typed in the wrong powder. I don't think (oh oh, that's not a good sign when I do that) it will make much difference in this situation since both powders are considered medium rate although Power Pistol burns a little faster. Most of the info I've found using loaddata.com and shootersreference.com list max loads of 8.0 to 8.5 grains for Power Pistol, well above my problem load of 7.3 grains.

All the other info is correct as far as my single brain cell can recall.

Still, a lot of the pointers and suggestions you guys are providing are giving me something to consider.

After doing more research on the web, one person had several case head separations one after another and traced the problem to over lubing the barrel and chamber. After cleaning out and drying the chamber, his problems went away. I did try some One Shot spray lube for a while to make it easier to resize my brass. So maybe I didn't clean it all off.

I also found a way to guesstimate head space using a fired primer in a resized case until I can get a proper set of go/no-go gauges (pics below). I inserted the case with a slightly protruding primer into the chamber and then cycled the lever until the bolt was closed, seating the primer the rest of the way. I then measured the combined case and primer length and compared that to the case length without the primer. I'm getting a difference of .0065-.0070" which I'm guessing is the head space. That's under the SAAMI spec of .0100" if I'm reading all their numbers right. Why couldn't they just put it in plain language.

DsGrouse is right - I'm using a Lee carbide die. Mine resizes most of the case down to .3730" diameter, not too much below factory ammo at .3750" below the bullet. All my new factory ammo also measures .3750" near the rim, but my factory and reload cases measure .3770-.3775" after firing. That transition from .3770-.3775" to .3730" is where my case head separated. It is also in the same place on the resized case I found with the crease/ring and had previously set aside.

My Henry's chamber is a little larger than the chambers in my Ruger and S&W 357 revolvers. Cases diameters are 3820" after firing in the Henry vs .3795" in the revolvers. So DsGrouse idea about work hardening, especially combined with the Henry's slightly larger chamber, might have been the cause in this case.

Thanks for all the suggestions. Since I'm only looking for a plinking round, I'm going to back off the load about .5-1.0 grains. I only lose about 100 fps which still gives me about 1200 fps MV. I'll follow up if the problem happens again with the reduced loads.

And anybody want a can of One Shot spray lube? Going to quit using it since it might have been a contributing factor.

My Bubba headspace gauge below.
Primer before seating it with the bolt

Primer after seating it with the bolt. You can still see it standing just a bit proud. I finished fully seating it with a hand primer and could feel move just a bit more until it was flush with or slightly below the base of the rim.

[rickhem]

I can see the pictures now.
My Square Deal has carbide dies, as does the other Square Deal for large primers. I've also got carbide for the .45Colt for my Rockchucker. I don't notice the resizing marks on the .45acp and the .40S&W cases, but I get similar marks on .38 special, .357 mag, and other straight wall cartridge cases when I resize. You can see how much of the case has entered the resizing die, or worded another way, how low onto the case the resizing ring has gone down as the case is pushed up into it. I once loaded some 148 DEWC bullets that must not have been sized properly, as they made a distinct bulge in the .38 case when seated flush. But never had an issue with case separation like you had. Those pics of your headspace measurement look like some of my cases when sized. Not all do that though.

Case separations in a bottleneck cartridge happen when you push the shoulder back too much, then the case stretches back out upon firing. Repeat that a few times and the case right above the head, gets thin and brittle from that back and forth. Eventually it just separates, almost always at that same place in the case. But in a rimmed straight wall case like the .357, I don't know what would stretch it. There's noting but axial expansion happening as the bullet leaves the case.

I keep having thoughts about you mentioning the chamber on the Henry being just a tad bigger, maybe that's part of the issue. I can see that adding to overworking the brass, but it would take a few cycles of shoot and reload for that to manifest itself.

[220]

Case separation is nearly always a head space issue.
Looking at the photo of the primer it appears to be massively out of spec.
I would be contacting henry or at least getting a gunsmith to put a set of go no go gauges in it to confirm.

[220]

Sorry just re read your post and realized the first photo was prior to chambering.
Does look like it may be within spec looking at the second photo.
I would still get the head space checked if you can as case separations are nearly always head space related.

[DsGrouse]

I changed the powder to power pistol

7.3 grns power pistol you are looking at 14354 psi and 1319.4 fps.
8.0 grns is 17508 psi and 1418.0 fps
9.0 grns 22675 psi and 1544.2 fps
10.00 grns is 28690 psi, and 1658 fps. It is also below the 25% Pmax.

I don't think this is a hot load issue, i think this is an issue with a piece of brass. I don't know if taking your load down 1/2 a grain will do much to stop a piece of brass failing.
the numbers for 6.8grns of power pistol
12,320 PSI 1241.5 fps. and 541 fpe.

[Travlin]

I used to get similar but not as bad marks when I loaded military .38 special cases using a carbide sizing die. I shot most of that brass many times using a load of 5.5 of Unique with my home cast hard 160 grain SWC. . I shot it in my Colt Trooper . I never had a loose primer or head separation of course that was shot in a revolver.

[azdover]

DsGrouse - thanks for the pressure info. What exactly is GRT? Looks like it might be a use tool for hand loading.