Incipient Case Head Separation

[Arkansas Paul]

Great presentation. Although I've been loading for about 3-4 years, I didn't really know what caused thinning of the brass near the base. I always just assumed that it was the brass wearing out. I had no idea that oversizing could result in that. I think I'll invest in a few Wilson gauges for the rifles I shoot to make sure everything is on the up and up. I've always just adjusted the dies according to the die maker's instructions and loaded.

I have had this problem with a rifle with excessive headspace. I had a NEF Handi Rifle in .280 and actually liked the gun. However, I couldn't get a handload to shoot to save my life. Factory ammo did fine, but even neck sizing, I couldn't get it to shoot a handload. it's gone now, but one time I fired it and opened the breech and it spit out about a half inch piece of the the case, leaving the remainder in the gun. I had to dig it out with a mini screwdriver. That was only the second time that brass had been loaded.

 

[DM~]

It doesn't matter if the case is "belted", "rimmed" or "rimless", the sizer die should be set so the case "headspaces" on the shoulder...

That's how you keep "case stretch" to a mininum.

DM

 

[gamestalker]

I've seen a number professional illustrations over the years relating to this particular topic, but none quite as elaborate and informative.

Great work Walkalong!

I'm one of those, who like your buddy, that like to squeeze every load I can out of my brass. So I have seen more than my fair share of incipient separations, and a few total separations. But I have calmed down some over the years, and now I will cull them out before they develop catastrophic failure. But I'm a stickler about getting my brass to chamber spec, and in spite of the fact that I generally load at worked up maximums, I manage to still get a good number of cycles from my brass using nothing other than a standard quality FL die, such as RCBS.

It isn't unreasonable to expect no less than 10 loads from just about any bottle neck brass if it is properly sized. And this number is conservative IMHO, as I average no less than 12 cycles from 7mm RM, which is often considered to have a shorter than average life span by some. Using nothing but standard factory brass, Win, RP, and even Fed commonly last me at least 12 cycles, and longer if I do my part..

GS

 

[Centurian22]

Walkalong, amazing write up! Thank you from a new reloader who hopes to avoid any potential case failures with the use of my handy dandy sharpened paper clip.

Gamestalker: I would love to hear your reloading process to see if there's anything I could be doing differently to extend my brass life. I'm only on my second loadings now but 10-12 loadings sure sounds a lot better and a lot more economical than 3-4. If you're willing to outline it feel free to PM me so as not to derail this thread.

Thanks.

 

[Walkalong]

I have a .35 Remington case I found at the range. I have used it to test velocities in my rifle with several different powders. It must have been fired 10+ times by now and has no signs of an internal rut. Not all have been max firings. I am using a home made "gauge" to get measurements on the shoulder for sizer die adjustments.



When it comes to case stretching and incipient case head separation it's all about how far you move the shoulder.

I recently used 10 .223 cases to do some velocity testing and they all lasted until the primer pockets got too loose. This happened anywhere from 8 to 12+ firings, and this was with using a Wilson case gauge to adjust the sizer. I adjusted the sizer so the brass was in the middle of the acceptable range in the gauge.

 

[Rule3]

Thanks again for the reply to by second post.

I guess it is the word INCIPIENT that has a scary ring to it!

Even though I have a goodly vocanilary for lernded me three R's I had to look it up.

beginning to come into being or to become apparent

 

[Walkalong]

Yep, scarier than "impending".

 

[Rule3]

Doom!:d

 

[Hondo 60]

Do you know how many loads he got out of those before they crapped out on him?

Number of firings may not be an indication of impending separation.
It "can" be, but it's not set in stone.
I've got some 223 brass that's been fired 5+ times.

About 2 months ago I had a separation on the 2nd firing.
And yes, I'm sure it was the 2nd firing.
I fired factory ammo & reloaded it once.

My load is 26.0 gr of Varget under a 55gr FMJ.
Hodgdon's data says 25.5 - 27.5(compressed), so I'm sorta in the middle.

 

[ants]

Walkalong, perhaps you might note that belted rifle cartridges 'headspacing' on the belt are notorious for short life and head separation, especially when shoulder pushed back too far.
Magnum pressures in belted cartridges certainly contribute to this. Those are the ones to which you pay strict attention. To detect the 'rut' or just the rough spot is a matter of practice.

 

[blue32]

Good info. I've got 15 firings and three trimmings on two lots of 260 brass that have at least 10 warm loads but I still can't feel/observe any signs of case head expansion. I've found primer pockets go before I see the former.

 

[Walkalong]

Walkalong, perhaps you might note that belted rifle cartridges 'headspacing' on the belt are notorious for short life and head separation, especially when shoulder pushed back too far.

Very true, and why most folks size them to "headspace" on the shoulder instead of the belt. Good point.

 

[Muddydogs]

Anyone interested in setting up there dies right to get the most life out of there brass need a way to measure fired cases and sized cases. The Wilson case gauges or similar type gauges are not the tool for this job, the Wilson type gauges are set to SAAMI specs and tell you if your brass is within SAAMI specs but what you are trying to accomplish with only setting the shoulder back a minimal amount might actually be outside SAAMI specs.

There are a few ways to measure correct shoulder set back for your particular firearm from trial and error where the brass is sized in small increments and then chambered in the firearm until the bolt closes correctly to actually measuring the cases. If one has the skill and tools a gauge or collar can be made like shown in Walkalong posts but for those of us that might not have the tools or skill to make our own then the Hornady Headspace gauge set or similar is the ticket.

A tool like the Hornady Headspace gauge and a Vernier caliper measures your fired brass from the bottom of the case head to a point on the shoulder. This point on the shoulder isn't exact and might not be the same between gauges of the same size but it doesn't matter, this measurement is for your firearm only. Once the measurement is known for the fired brass the sizer die can be set up by sizing cases and measuring them until the sizer die is adjusted to set the shoulder back the desired amount, usually .002" or so thousands. The nice thing about a tool to actually measure the headspace and get a real number is this number can be used in subsequent reloading seasons to make sure the sizer die is tightened into the press the same each time. It's also handy to be able to measure different brands of brass while sizing them as some brands might need a little more or less adjustment on the sizer to get the correct headspace.

 

[243winxb]

Belted rifle cartridges headspacing- - A 7mm Rem Mag that has brass sized to give a crush fit , on bolt closing , may cause another problem.

A sloppy maximum spec chamber (.015") may allow the brass right in front of the belt (towards the case mouth) become unsupported . This makes another problem, as brass expands from repeated firings.

A member, Gamestalker, had this problem when only neck sizing his 7 mag.

 

[Muddydogs]

Good info. I've got 15 firings and three trimmings on two lots of 260 brass that have at least 10 warm loads but I still can't feel/observe any signs of case head expansion. I've found primer pockets go before I see the former.

I too find that primer pockets go before I see any sign of case head separation and I have 10 plus firings on some 7mm rem mag brass that are just starting to get loose primer pockets.

 

[fguffey]

Anyone interested in setting up there dies right to get the most life out of there brass need a way to measure fired cases and sized cases. The Wilson case gauges or similar type gauges are not the tool for this job, the Wilson type gauges are set to SAAMI specs and tell you if your brass is within SAAMI specs but what you are trying to accomplish with only setting the shoulder back a minimal amount might actually be outside SAAMI specs.

Not true, it was not that long ago reloaders were calling the Wilson case gage a 'drop-in-gage'. From the beginning the Wilson case gage was designed as a datum based tool. I understand it is cool to have 'home-made' tools but the datum is nothing more than a round hole without a radius. A reloader with a few shop skills and has the ability to drill a straight hole can make a comparator and a case length gage.

Wilson type gauges are set to SAAMI specs and tell you if your brass is within SAAMI specs but what you are trying to accomplish with only setting the shoulder back a minimal amount might actually be outside SAAMI specs

That sounds great but a reloader using the Wilson case gage is not checking cases for a chamber he may not have' he is checking cases fired in his chamber. I would suggest the reloader measure the length of the case before firing and again after firing. Measuring before and again after firing turns what ever tool the reloader is using into a comparator. It is possible to compare the comparator measurements with SAAMI specifications if the reloader can verify the tool. If the tool has a datum with a radius it gets complicated.

F. Guffey

 

[fguffey]

There are a few ways to measure correct shoulder set back for your particular firearm from trial and error where the brass is sized in small increments and then chambered in the firearm until the bolt closes correctly to actually measuring the cases. If one has the skill and tools a gauge or collar can be made like shown in Walkalong posts but for those of us that might not have the tools or skill to make our own then the Hornady Headspace gauge set or similar is the ticket.

measure correct shoulder set back

And then there is that part about shoulder set-back; reloaders assume the shoulder is set-back when sized and they assume the shoulder of the case moves forward when fired. If the shoulder of the case moves forward when the firing pin strikes the primer the case stretches between the case head and case body. When sizing my cases the shoulder does not move. Yes the case length shortens between the shoulder of the case to the case head when sized but, again, that does not mean the shoulder moved.

F. Guffey

 

[Muddydogs]

And then there is that part about shoulder set-back; reloaders assume the shoulder is set-back when sized and they assume the shoulder of the case moves forward when fired. If the shoulder of the case moves forward when the firing pin strikes the primer the case stretches between the case head and case body. When sizing my cases the shoulder does not move. Yes the case length shortens between the shoulder of the case to the case head when sized but, again, that does not mean the shoulder moved.

F. Guffey

So it magically gets shorter or are you saying you're compressing the body of the case? Not sure what you're trying to say here and I read your post a few times but it reads like a riddle.

What I was trying to get across is you just can't drop the case into into a go no go gauge and get any real meaningful data. If you want to take the time to reload good ammo then a go no go gauge is basically worthless and not needed if you are measuring your head space and sizing cases to fit your rifle.

 

[fguffey]

What I was trying to get across is you just can't drop the case into a go no go gauge and get any real meaningful data.

You lost me on that one when you said "you just can't" because I can and the other part that is confusing is the part where you say "drop a case into a go-gage"; I find that impossible because the case gage is a case gage it is not a head space gage because the case does not have head space.

I can get real meaningful data from a case gage because it is a datum based tool. From the beginning I have followed the instructions from Wilson. Wilson instructions for the case gage has been with us since 1954. Wilson suggested using a straight edge with the case gage, for me it was automatic, I added the feeler gage. When using the Wilson case gage I get reading in thousandths as in .000". I also use a flat surface like a lay-out table/plate.

In the original instructions Wilson made it clear the little rule in the shirt pocket was a pocket rule and it can be used as a straight edge; again, rather than use a wild guestimate with my thumb nail I use the feeler gage. It is not necessary to measure the length of the case from the shoulder to the case head but when measuring the length of the case before firing and after firing a reloader can get very meaningful measurements; and then there is measuring after sizing when returning the case to minimum length/full length sized or when using the length of the case from the shoulder to the case head to off set the length of the chamber from the shoulder to the bolt face.

No riddle; convince me the shoulder moves when sized and or fired. If there is a riddle it comes when I fire 30/06 cases in a chamber that is .002" longer than a field reject length gage. If the shoulder moved .016" I would have cases that stretched .016" between the case head and case body. I off set the length of the chamber with the length of the case .014" from the shoulder to the case head.

F. Guffey

 

[Walkalong]

fguffey is correct, you can use the Wilson gauge to check shoulder position before firing, after firing, before sizing, after sizing, and get real meaningful numbers to go by concerning your chamber and how much you are moving the shoulder.

 

[Muddydogs]

fguffey is correct, you can use the Wilson gauge to check shoulder position before firing, after firing, before sizing, after sizing, and get real meaningful numbers to go by concerning your chamber and how much you are moving the shoulder.

Wait a minute you are moving the shoulder when you size?

 

[Bart B.]

When sizing my cases the shoulder does not move. Yes the case length shortens between the shoulder of the case to the case head when sized but, again, that does not mean the shoulder moved.

This is the confusing part of this whole thread I think Muddydog is referring to. Walkalong's stuff is the icing on this case resizing cake, but I cannot grasp Guffey's claim.

For example, here's a picture with a 300 Win Mag case on the left with a blue line on its shoulder. Next to it is the same case full length sized in a 30-338 Long Neck Mag die showing its shape after resizing. My question is, according to Guffey's comments, what line is now the resized case shoulder?



The red line on the resized case is where the original shoulder metal is on the resized case, if Guffey is right and the shoulder doesn't move

The green line is where I (and so darned many others) think the shoulder is on the resized case.

I though about showing diagrams of a 280 Remington case being resized to a 7-08 Rem case then trimmed. It would be much the same. But I don't have one of each to show the same thing with different cartridges. But a .30-06 case being resized then trimmed to a .308Win case would do as well.

Conventional thinking is the shoulder is that case part between the front of the case body and the back of the case neck. Regardless if it's moved by sizing dies or firing in a chamber.

 

[Bart B.]

Meanwhile, back to topic.......

Hatcher wrote in his book the Mauser 98 and Springfield 1903 rifles could set back chambered case shoulders a bit by chambering alone; .0045" with the 98 and .012" with the 1903. Win 70's didn't do that in my tests.

I've observed .308 Win case shoulders setting back from firing pin impact. A few thousandths with brass cases and several thousandths for nickel plated ones. All with reduced loads more than 10% below max. Primed cases without powder and bullet did the same thing. All done in Win 70's.

 

[fguffey]

Wait a minute you are moving the shoulder when you size?

Muddydogs, I said I found it impossible to move the shoulder back when sizing a case. I said I can move the shoulder back as in shortening the case from the shoulder to the case head but I said I can not move the shoulder back with case body support.

I can move the shoulder back without case body support,; problem, the case takes on the appearance of an accordion with bellows at the case body/shoulder juncture.

When I size a case I shorten the distance from the shoulder of the case to the case head; again, the shoulder on my cases when sizing does not move. When the shoulder moves: If the shoulder is attached to the case body when the shoulder moves expect stretching between the case head and case body. Stretching between the case head and case body is the beginning of insipient case head separation. And yes; the case head can separation on the first firing.

F. Guffey

 

[243winxb]

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