357 Case Head Separation

[azdover]

A long post but I'm trying to get as much info out there for my questions.

I had a case head separation today with a 357 Magnum handload in my Big Boy Steel.
- 158 gr Xtreme Plated SWC
- Twice fired Federal brass
- Federal 200 Small Pistol Primers
- OAL 1.590'
- Medium taper crimper
- 7.3 gr Power Pistol not CFE-P

I was using Xtreme's load data for their other 158 gr plated bullets for reference since they didn't specifically list a load for their SWC. Their other bullets listed 7.6-7.7 grs max with a muzzle velocity just shy of 1300 fps and max pressure of about 29,000-30,000 psi although they don't list a barrel length. I figured 7.3 grs was safely below the max. I had worked up from 6.4 grs to 7.3 grs in both revolvers and my rifle and didn't see any problems of overpressure - no flattened or cratered primers, no sticky cases during extraction. I was getting about 1000 fps from my 5 1/2" and a 7 1/2" revolvers and about 1300 fps from the 17 1/2' barrel on the Big Boy, both with single digit SDs.

I had already fired about 15 rounds through the rifle when this happened and was recording data with a Garmin Xero C1 Pro. It showed the shot at 1319 fps. There was no muss or fuss - the only indication I got the case head had separated was a FTF for the next round. When I turned the rifle on its side to clear the next round, the case head also fell out and I noticed the rest of the case still stuck in the chamber. When I got home to clear the chamber, the rest of the case fell out by itself when I opened the bolt.

I've been hand loading pistol cartridges for the last 25-30 years. Nothing fancy or fire breathing. Other than a few split cases or light primer strikes, I've managed not to blow myself up (as my granddaughter once informed me I might) - at least not yet. This is a first for me.

So, my question is - what can cause this? A quick web search pointed to excessive head space so I guess I need to learn how to check that.

I don't think the load was a problem. It's toward the upper end of all the info I could find, but looks pretty mild for 357 Magnum.

I usually only reload my brass 5 times max before replacing it. I had previously found a resized case that had an obvious crease right where the problem round separated and had set that aside. None of my other resized brass or reloaded rounds show that same crease. Below are measurements of different cases near the base and about halfway up the case, starting with a factory round for reference and compared my handloads.

Top to bottom
Federal factory 158 JSP .3750" .3750"
Unfired handload 158 SWC .3775" .3730"
Sized handload case .3775" .3730"
Fired handload case .3775" .3830"
Separated case .3770" .3820"
Creased sized case .3775” .3730"

I use Lee dies for my reloading. Is it possible that the resizing die is too small and is necking the case down too much - maybe weakening the case with excessive bending and creating a stress point? Kind of like flexing a thin piece of metal back and forth until it finally breaks?

Open to all suggestions,
Pete

[BigAl52]

On the bottom piece of brass I see what appears to be a ring around the brass. Am I seeing that correctly?

[azdover]

Yup. That’s the one I had noticed previously after sizing some brass. It’s measurements is the last entry in my list of measurements.

[BigAl52]

That doesn’t look good to me. Ive got Dillion Square Deal dies and RCBS single stage carbide sizing dies and I dont get anything like that on my brass. Does it do that on all the brass when you resize it or just every once in a while

[azdover]

First time I've ever seen that crease/ring on a resized case. I didn't notice anything like that on the case that separated but it may have been there and I just didn't catch it. I've checked some of my other cases, both fired and resized, and haven''t found any more. It looks like the crease/ring occurs where the sizing die stops resizing the case just short of the base of the shell.

After a little more research, it looks like head case separation can happen occasionally in 357s with excessive head space, particularly rifles but not revolvers. Looks like it's time to whip out the plastic and give Brownells some more business for a set of go/no-go gauges.

[5shot]

I've never seen a case separation like that in a straight wall pistol cartridge and don't know anything about Xtreme bullets. Your fired rounds are a couple thousands bigger than the cases I just measured but your handgun velocities don't seem to be out of line. Looking in the Hodgdon manual I see their maximum load of CFE Pistol under the 158 XTP is 6.9 gr for 33,700 PSI. Could it be that the combination of seating depth, primer and powder charge is too hot?
The Savage 99 was known for case separations with warm loads. I helped a guy at the range extract a case from his .250/3000 Savage a couple weeks ago. If the Henry action exhibits that same "springyness" with higher pressure loads could the case walls be clinging to the chamber while the case head is backing up a bit? Just thinking out loud here...
CFE is a relatively fast burning powder in the .357 case and I wonder if it doesn't go from mild to wild quickly. I've got some .357 brass with well over 20 loadings but after a half dozen or so of full throttle stuff it gets "retired" for use with mid-range loads.
For what it's worth....

[rickhem]

Unfortunately, my work firewall is blocking the pictures from being viewable here. I'll have to check this out when I get home later. But that said, glad you are safe and you did the right thing by stopping and figuring out what happened.

Having been experimenting with some stout loading trials on my own .357 BBS, I'm paying attention here. Most of my warmer loads have been with either Lil Gun, or 296, and honestly way more Lil Gun than anything. So far, I haven't had any issues with the brass, and the brass I've been using for these warmer loads is a mix of RP, PMC, and GFL (Fiocchi). I say mixed because I load the same load in different cases, but do keep them segregated by headstamp during the process. Sometimes one specific case seems to give better results.

I've had case head separations in my AR15, shooting .223, and the first time it caught me completely off guard. The other guys on the line treated it like no big deal, a few had a little removal too for the top of the case that was still stuck, and the general consensus was that "it happens". I even got an alibi out of it. So I doubt your rifle has any damage, if that is a concern.

A .357 headspaces on the rim, so the condition that would cause a case head separation in a bottleneck cartridge is completely different than what you had. I'm going to have to get back to this after I can see the pictures and think about it a little.

[CT_Shooter]

First time I've ever seen that crease/ring on a resized case. I didn't notice anything like that on the case that separated but it may have been there and I just didn't catch it. I've checked some of my other cases, both fired and resized, and haven''t found any more. It looks like the crease/ring occurs where the sizing die stops resizing the case just short of the base of the shell.

I've marked this image to suggest the reloading process may be the cause, as you suspect. It seems that the reloaded cases have each been affected somehow. Interesting problem. Please keep us posted. Thanks.

What's causing this mark on the Case?

Handload Cases.jpg (111.02 KiB) Viewed 3471 times

[DsGrouse]

Let me guess: you are using carbide resizing dies. I get a similar ring. I don't load my plated that hot, most of my shooting is subsonic. My load is 4.8 grains of cfe p. coal 1.455 for an average of 944.5 fps.

I'm thinking of going to a steel-sizing die because of this ring issue. I get this same issue with Lee, RCBS and redding carbide dies.

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.

Looking at your load data, you don't have a high pressures according to GRT. That is, if, IF, your brass holds the same 27.30 grains of h20 that mine does.


It looks like peak pressure is 18,230 psi.

From what I gather, a lot of that is due to Henry. The initial bullet jump reduces pressure compared to a similar system like a revolver. I didn't bother adding in the bullet jump into this equation as your rifle might be different than mine.

with a 180 grain bullet, 1.575 coal, my bullet jump is 0.3500 to the lands. That brings my peak pressure down quite a bit.

[CT_Shooter]

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

[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]

...
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.

[DsGrouse]

...
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.