What is this???

J

JDBraddy

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Minuteman
Apr 15, 2011
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San Antonio, TX.
#1
I fired a round yesterday, and noticed smoke from around the bolt, it was difficlut to lift the bolt handle, then the case came out in two pieces (see picture below). This was not a hot load, 7mm-08, 150gr SMK, 42gr Alliant 2000-MR, Fed-210 primer, 2.800-OAL, Remington brass, chronographed at 2,634fps. When I went home, I examined the brass, it looked like it had been cut in half with a band-saw. I looked at the rest of this lot of brass. It's not new brass, it started out as factory ammo, and has been fired and reloaded six or seven times. Out of a hundred pieces, I found about twenty that had a visible ring of discoloration at about the same point where the seperation occured. I've been reloading almost thirty years now, and have never encountered this before, what is it?

11110893426_fd38168b01_b.jpg
 
#2
It's called case head separation. Usually from oversizing your brass, bumping the shoulder too far back. In essence, crushing the case too much, the brass blows forward when fired, and cases separate, the rest of your brass will likely do the same thing, time for new!
 
#5
I had this happen on some .223 reloads I had done for my AR a few years ago. I had used some of Federal's factory brass (wasn't FGGM, it was from their 100 rnd bulk pack). I quit using the brass immediately. This was only on the brass' first reloading.
 
#6
I'm using an RCBS full length die, I used an RCBS micrometer to measure, and adjusted the die to where it bumps the shoulder back about three thousanths of an inch on a fired case. The case necks have been turned to a thickness of 12 thousanths of an inch.
 
#8
As stated above you are over resizing your cases and bumping the shoulder back too far, this makes the case shorter than it needs to be and creates excess head clearance.

Head clearance is the "air space" between the rear of the case and the bolt face, and the general thumb rule is .001 to .002 shoulder bump or head clearance on a bolt action and .003 to .004 on a semi-auto.

HEADCLEARANCE-a_zps1a9a1011.jpg


Below is a animated image of a cartridge case firing and the brass case stretching to meet the bolt face.

HeadClearance_zpsf30a3af1.gif


If you control your full length resizing and only bump the shoulder of the case back .001 to .002 the brass is elastic and will stretch this minimum amount and then spring back to its original size when fired.

You need a Hornady Cartridge Case Headspace gauge, you measure your fired cases and only resize them the minimum amount and you will not have case head separations.

gauge002_zpsd2792ffa.jpg


I use Redding Custom Shell Holders to control shoulder bump below, the dark shell holder has a +.004 on the top of the shell holder. This shell holder is .004 (four thousandths) taller than a standard shell holder, the set contains 5 shell holders and each one is progressively .002 taller than the next one.

shellholders_zps0f9bb695.jpg


You do not need these shell holders to make the die adjustments, and you can just use feeler gauges between the shell holder and the bottom of the die as spacers for setup.

In other words the instructions for your dies are written to make sure a resized case will fit any chamber and the instructions can cause you to over resize your cases. By adjusting your dies for "YOUR" chamber the cases will last "MUCH" longer.

Below is a exaggerated example of full length resizing, pay attention to the blue, red and green lines. When resizing you can actually make your cases "LONGER" than their fired length with excessive clearance between the die and the shell holder. The object is to just make the cartridge case one or two thousandths shorter than the chamber headspace and let the bolt close without resistance. (minimum clearance)

shouldersetback_zps59bf1b04.jpg


I inspect my cases with a RCBS Case Mastering Gauge and check for thinning in the base web area. And in 46 years of reloading I have never had a case head separation, by knowing what to look for before it happens.

RCBSCMG_zpsb95d3710.jpg


Below is an example of a SAAMI commercial case being fired in a Military .303 British chamber. At maximum military headspace you can have as much as .017 head clearance and the case will stretch badly.

headspacestretch-c_zps8f362fcb.gif


With proper fireforming techniques and allowing the case to properly headspace on the shoulder there is no room for the case to stretch.

zeroheadspace_zpsbaf7579c.jpg


The .308 cases below were resized with the dies setup as per the instructions and the press reaching cam over. This is only an example and actual case life will depend on adjusting your dies for minimum shoulder bump. The rifle used for this test was a new Savage rifle and had tight headspace meaning no more the .002 over the GO headspace gauge.

308fail-1_zps30d387ab.jpg


308fail2-1_zps3ca31f6b.jpg
 
Last edited:
#9
I have had this case head separation happen on 2 brand new pieces of remington 7mag brass recently. The rest of the batch has been fine through two firings though.. I'd say it's time to get some new brass. Some loads will go 20 firings in a given caliber and others you may only get 5.... My 300 RUM averages about 7 firings before I move on to new brass just because I consider it to be cheap insurance. I once had a 25/06 that developed a headspace issue to the point that it wiped out some brass on it's first firing as well.
 
#10
Classic Casehead Separation.

Causes:
-You're resizing the cases more than absolutely necessary and they are stretching during every firing.
-The 20 degree shoulder allows the brass to flow forward during firing, which is the reason for case trimming. That brass you're trimming off has to come from somewhere....

Neither is totally unavoidable. You've got 6-7 reloads which is reasonable. If it were me, I'd bin the entire lot, as they can't be far behind, presuming they've all been treated the same.
 
#12
Toast said:
Damn Big Ed. You got the Family Guy animation going and everything. You're like Luke Haag. What an incredible explanation. Thanks.
Click to expand...

Actually I learned about excess headspace in my younger days, in dimly lit bars being served by unscrupulous bartenders.

excessheadspace_zpsf2634b56.jpg




LaughingSmiley_zps51f85375.gif
 
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#13
Thanks Guys, Think what I'll do is use the cases with visible rings to reset my sizing die to bump the shoulder 0.001" or less, then discard them. Will also take the rifle to a gunsmith tomarrow to have the headspace checked. Then reload the remaining brass and see what happens. Guess every once in a while even old dogs have to learn a new trick!
 
#14
JDBraddy said:
Thanks Guys, Think what I'll do is use the cases with visible rings to reset my sizing die to bump the shoulder 0.001" or less, then discard them. Will also take the rifle to a gunsmith tomarrow to have the headspace checked. Then reload the remaining brass and see what happens. Guess every once in a while even old dogs have to learn a new trick!
Click to expand...

JDBraddy said:
About a week or two ago, I was cleaning this rifle and my identicle .308 Win, and had the bolts lying side by side, it's possible I might have gotten them confused, and put the wrong one back in each rifle, could this be the cause.
Click to expand...

It be nice if you would tell the whole story and not leave the best part out.

AccurateShooter.com By JDBraddy
What is this?
 
#17
The advice you've gotten above is spot on, but I'd like to add a recommendation.

The stretching of your cases has resulted in thinning the case wall at the spot you see the rings (and got one separation). Before throwing out the other cases, check them to see/learn how in the future to find cases in danger of separating . . . before they separate.

Take a paper clip, straighten it out, then using a needle nose plier bend one end to a 90 degree angle about 1/8" or less long. Insert that end inside a suspect case and "scrape" that bent tip up and down the inner wall. You will (most likely) feel an indentation where the ring appears on the outside of the case.

I've incorporated that test into my case prep to differentiate between shiny rings sometimes made by the resizing die (usually lower down than yours), and developing case separation.
 
#18
I will also add that the above advice and explanations of case head separation are spot-on.

Twoboxer is also correct in how to detect a soon-to-be separation. If your cases are showing the bright ring in the OP's photo, they are too far gone and should be discarded. The bent paperclip method will detect the indentation of the case wall thinning before a visible bright ring manifests itself.

Throw out all of the cases with the visible bright ring and check all of the rest.

Paul
 
#20
The OP JDBraddy needs to find out if he inadvertently swapped bolts on his .308 and 7mm-08 and if this is causing the problem.

Excessive head clearance is what causes case head separations.

HEADCLEARANCE-a_zps1a9a1011.jpg
Cheap bastards headspace gauges.................

Take a new unfired case or a full length resized case and measure its length and write it down.

303gauge_zpsb1e333a7.jpg


Next take a fired spent primer and start this primer into the primer pocket with just finger pressure.

303primer_zpsae8fdb45.jpg


303primera_zps612343f9.jpg


Now take this test cartridge and chamber it in the rifle, slowly closing the bolt. The bolt face as the bolt closes will seat the primer. Remove the case and measure the case length again, the case is going to tell you a story.

The amount the primer is protruding from this test cartridge is head clearance or the "air space" between the rear of the case and the bolt face. Subtract the first case measurement from the second case measurement and this is your head clearance in thousandths of an inch.

hedspace-b_zpsce06e3e4.gif


enfieldHS_zps99b67ad8.jpg


The primer trick will work with any rifle and type cartridge, forgive me I collected Enfield rifles and most of my illustrations are for the British .303 Enfield rifle. I have headspace gauges for most of my rifles but you you do not need head space gauges to figure out your head clearance.

The only difference between cartridge designs is the distance from the bolt face to the datum line.

Headspace_2_lg_zps3fea821e.jpg

Headspace_1_lg_zpsdd7501b6.jpg
 
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#22
I dont think it is worth running them through the die as one may break off and get stuck there? a cleaning rod and brush "may get it out" ? just "bump the good brass and toss the rest.

also the bolts may have the last 4 serial # digits on them to match them up with the action?
 
#23
BuzzBoss915 said:
How lucky we are to have bigego solving these things for us! BB
Click to expand...

Headspace is also the distance between your ears and what that space is filled with.

If I may be so bold as to make a suggestion...............

When you drink tequila at home, don't cut the lemon slices so big and suck on them so long.

The Enfield rifle below has had the headspace set from just kissing the rear of the case to .010 over military maximum with the aid of removable bolt heads. This amounts to .006 under the minimum of .064 and .010 over the maximum of .074. Having collected many Enfield rifles you tend to learn a great deal about headspace and not let it effect your ego like some posters comments above.

enfieldHS_zps99b67ad8.jpg


Picture009_zpsa5f7e7dd.jpg
 
Last edited:
#26
BuzzBoss915 said:
Au contraire, mine a totally innocent observation! Why such a snippy little bitch, today? BB
Click to expand...

Let me know how many "likes" you get for your "innocent observation".

And remember, don't suck on big lemons and make postings while your ego is so bruised.

Your motives and anger are very clear....................................

typingdeath_zps1a95d266.gif
 
#27
TOP PREDATOR said:
nice posts bigedp51

IMO (though not worth much), sticky worthy for a whole lotta information with great explanation of the topic and other things that happen in the chamber / brass when firing.
Click to expand...

I'm not sure how to take your posting, the OP either mixed up his bolts on the two rifles or else his dies are not adjusted correctly. Either the rifles headspace is off or the cartridge case headspace is off and if he swapped bolts its all of the above.
 
#28
take it well, you described very well a whole bunch of stuff to look out for, how it happens, how to check for it using some simple ways, plus what happens in a sizing die.

i got a whole bunch of great info out of it, never thought of the loose primer trick as a tangible way of measuring to better / more accurately set up my dies.

usually i check for separation the same way as the paperclip post above, scraping the inside with a hair pin broken off in the center of the bend so there's a little hook on the end that will catch on any type of crack on about shot #5.
 
#29
bigedp51, I for one am very thankful for the way you explained this and your ideas on headspace measuring. I have heard most of this before, but it is good to see your layout and your pics to illustrate clearly your points.

OP, if indeed it is true that you may have swapped bolts, then you would have been better off to have mentioned that possibility in your original post. Shame someone had to come across that post in another thread...
 
#30
Sniper Uncle said:
bigedp51, I for one am very thankful for the way you explained this and your ideas on headspace measuring. I have heard most of this before, but it is good to see your layout and your pics to illustrate clearly your points.

OP, if indeed it is true that you may have swapped bolts, then you would have been better off to have mentioned that possibility in your original post. Shame someone had to come across that post in another thread...
Click to expand...

Ditto here Ed.
 
#32
JDBraddy said:
Took both guns to a gunsmith today, each rifle had the correct bolt in it, and headspace of both rifles are within spec. Also had the bolts marked, so there will be no chance of mixing them up in the future.
Click to expand...

Good to hear. You may have gotten some bad brass, or you may need to re-check your sizing methods and make sure you are not bumping the shoulders back as far. You definitely need to check the interior of your brass for a "groove" like others have suggested, with a hair-pin or paperclip---sharpen it to a point and put about 3/16 or so of a bend in it so it "scratches" the inside of the case well.
 
#34
I measured each, and chose five of the longest cases, each chambered in the rifle without resistance, so I set the sizing die so that it touches but does not bump the shoulder at all, in fact a couple of these cases actually grew a thousanth longer when sized, I assume because of the neck expantion ball pulling upward on the inside of the neck/shoulder junction as the case was extracted from the die. I then resized all the cases and they are in the tumbler removing the lube now. Unfortunately, I work all weekend, so will have to wait till next week to load an fire them again.
 
#36
Setting up a Hornady Cartridge Case gauge to read actual cartridge headspace.

Colt AR15 5.56 Field Gauge II, 1.4736

headspacegauge006_zps3cdabdf4.jpg


Close enough, the headspace gauge is in the Hornady gauge and only reading .0001 (one ten thousandths) off. I placed a .010 feeler gauge between the Hornady gauge halves and locked the set screw to calibrate the gauge and read the same as the headspace gauge.

headspacegauge_zps14d3b71f.jpg


New unfired Federal M193 5.56 cartridge, civilian GO gauge is 1.464 so new ammunition is approximately .002 shorter than minimum headspace.

headspacegauge002_zpscc227fb8.jpg


Fired case from my AR15, civilian NO-GO is 1.467 and military NO-GO is 1.4706. So remember your using civilian reloading dies, and it is very easy to over resize the case.

headspacegauge005_zps20685e73.jpg


Resized case, .002 longer than factory loaded ammunition to make the brass last longer.

headspacegauge004_zps4465b7bc.jpg


1.4675 - 1.4645 = .003 shoulder bump and the case is .003 shorter than actual chamber headspace length.


no_lemons_zps4cd400c2.jpg
 
Last edited:
#38
What no one has yet mentioned, even though the headspace issue is reasonable, is that the separation is much farther out from the web as usual. Normally the separation is about 1/4-to 3/8th inch above the case cannelure. This separation pictured is almost half-way up the case wall. That to me is most peculiar. See the added picture at the beginning of the replies that shows the usual location and compare the two. Anyone have an explanation for that?
 
#40
I hadn't really thought about it until you raised the question, FNP, but you are correct in your observation.


former naval person said:
What no one has yet mentioned, even though the headspace issue is reasonable, is that the separation is much farther out from the web as usual. Normally the separation is about 1/4-to 3/8th inch above the case cannelure. This separation pictured is almost half-way up the case wall. That to me is most peculiar. See the added picture at the beginning of the replies that shows the usual location and compare the two. Anyone have an explanation for that?
Click to expand...

In the chart and pictures below, the case separation height does change between brass manufacturers, I think, indicating different brass hardness characteristics between manufacturers. I noticed the Federal ones to be the highest up the case.

bigedp51 said:
As stated above you are over resizing your cases and bumping the shoulder back too far, this makes the case shorter than it needs to be and creates excess head clearance.

Head clearance is the "air space" between the rear of the case and the bolt face, and the general thumb rule is .001 to .002 shoulder bump or head clearance on a bolt action and .003 to .004 on a semi-auto.

HEADCLEARANCE-a_zps1a9a1011.jpg


Below is a animated image of a cartridge case firing and the brass case stretching to meet the bolt face.

HeadClearance_zpsf30a3af1.gif


If you control your full length resizing and only bump the shoulder of the case back .001 to .002 the brass is elastic and will stretch this minimum amount and then spring back to its original size when fired.

You need a Hornady Cartridge Case Headspace gauge, you measure your fired cases and only resize them the minimum amount and you will not have case head separations.

gauge002_zpsd2792ffa.jpg


I use Redding Custom Shell Holders to control shoulder bump below, the dark shell holder has a +.004 on the top of the shell holder. This shell holder is .004 (four thousandths) taller than a standard shell holder, the set contains 5 shell holders and each one is progressively .002 taller than the next one.

(sorry, I removed this photo from post, as I exceeded the pic limit in a post...)

You do not need these shell holders to make the die adjustments, and you can just use feeler gauges between the shell holder and the bottom of the die as spacers for setup.

In other words the instructions for your dies are written to make sure a resized case will fit any chamber and the instructions can cause you to over resize your cases. By adjusting your dies for "YOUR" chamber the cases will last "MUCH" longer.

Below is a exaggerated example of full length resizing, pay attention to the blue, red and green lines. When resizing you can actually make your cases "LONGER" than their fired length with excessive clearance between the die and the shell holder. The object is to just make the cartridge case one or two thousandths shorter than the chamber headspace and let the bolt close without resistance. (minimum clearance)

shouldersetback_zps59bf1b04.jpg


I inspect my cases with a RCBS Case Mastering Gauge and check for thinning in the base web area. And in 46 years of reloading I have never had a case head separation, by knowing what to look for before it happens.

RCBSCMG_zpsb95d3710.jpg


Below is an example of a SAAMI commercial case being fired in a Military .303 British chamber. At maximum military headspace you can have as much as .017 head clearance and the case will stretch badly.

headspacestretch-c_zps8f362fcb.gif


With proper fireforming techniques and allowing the case to properly headspace on the shoulder there is no room for the case to stretch.

zeroheadspace_zpsbaf7579c.jpg


The .308 cases below were resized with the dies setup as per the instructions and the press reaching cam over. This is only an example and actual case life will depend on adjusting your dies for minimum shoulder bump. The rifle used for this test was a new Savage rifle and had tight headspace meaning no more the .002 over the GO headspace gauge.

308fail-1_zps30d387ab.jpg


308fail2-1_zps3ca31f6b.jpg
Click to expand...

JDBraddy said:
I fired a round yesterday, and noticed smoke from around the bolt, it was difficlut to lift the bolt handle, then the case came out in two pieces (see picture below). This was not a hot load, 7mm-08, 150gr SMK, 42gr Alliant 2000-MR, Fed-210 primer, 2.800-OAL, Remington brass, chronographed at 2,634fps. When I went home, I examined the brass, it looked like it had been cut in half with a band-saw. I looked at the rest of this lot of brass. It's not new brass, it started out as factory ammo, and has been fired and reloaded six or seven times. Out of a hundred pieces, I found about twenty that had a visible ring of discoloration at about the same point where the seperation occured. I've been reloading almost thirty years now, and have never encountered this before, what is it?

11110893426_fd38168b01_b.jpg
Click to expand...

The OP says that he had 20 or so cases out of his brass that seemed to have this issue. I didn't see if he posted anywhere whether this brass was all the same lot number, but I would guess it wasn't. Maybe he does have a bad box of brass mixed with his others.
 
#41
former naval person said:
What no one has yet mentioned, even though the headspace issue is reasonable, is that the separation is much farther out from the web as usual. Normally the separation is about 1/4-to 3/8th inch above the case cannelure. This separation pictured is almost half-way up the case wall. That to me is most peculiar. See the added picture at the beginning of the replies that shows the usual location and compare the two. Anyone have an explanation for that?
Click to expand...

The brass will stretch and thin at the softest area of the case and chamber pressure will push the harder and thicker part of the case to the rear. The OPs brass was Remington and thicker in the base than other brands of brass and just stretched further up the case where the brass was thinner. If the OP had used Winchester brass which is thinner the case would have separated lower on the case. Remington cartridge cases are built Ford tough.

Even an anchor chain is only as strong as its weakest link, "former naval person".
 
Last edited:
#42
Mad_Charlie said:
Any time I have incipient case head separation from cases used in my AR they are located high like that, can't explain why...
Click to expand...

Sniper Uncle said:
I hadn't really thought about it until you raised the question, FNP, but you are correct in your observation.

In the chart and pictures below, the case separation height does change between brass manufacturers, I think, indicating different brass hardness characteristics between manufacturers. I noticed the Federal ones to be the highest up the case.
Click to expand...

Brass quality, hardness and chamber diameter will effect where the case starts to thin and separate. Military grade milspec cartridge cases are made from higher quality brass and are also harder in the base than their civilian counter parts. This is why Lake City cases are preferred and last longer than other cases.

556hard-a_zps7570e6b0.jpg


hardness-a_zps8d54ad66.jpg
 
#45
Outstanding visual explanations. Always helps when ya get to see exactly what someone's talking about for sure. This has absolutely gotta be a sticky. Doesn't get much better than this. Thx.
 
#47
I am new here and am amazed at the incredible amount of knowledge that you guys have. Thank you, and I would also like to put in a vote to make this a sticky.
 
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