Case head seperation

[T-shooter]

Try measuring a few of your cases in several places before and after resizing to see how much you are working the brass. You can lightly scratch a mark on the outside. Using a marker, the marks may come off when resizing with lube.

 

[T-shooter]

Just think, was all of this brass from the same lot? You might send a few of the bad ones back to Lapua to be tested. They could be too hard or brittle and could also be a bad alloy mix or improperly annealed.

 

[savagedasher]

Case head is normall a product of over working the brass . When you size the brass with excess shoulder set back or diameter All your are doing is. Is makeing the pressure push the case shoulder foward. From the bolt face . Proper sizeing dies for the chamber is a must . Larry

 

[Ned Ludd]

you need reloading lessons. find someone who knows what they are doing to show you the fundamentals before you hurt yourself.

This is ridiculous BS, Richard. Why don't you just bow out of this thread if that's the best you have to offer.

 

[jsthntn247]

Agreed, it sounds like jsthntn247 is following the commonly prescribed fundamentals, does not seem to be anything wrong with his process.

jsthntn247, the only thing that seems a bit odd is your headspace measurements. I also use mitutoyo calipers + hornady gauge and my 223 cases measure around 1.460 fired. Are yours really 1.260? If so, perhaps we are using different inserts with the hornady comparator. I am using the one that says 'A330'.

This is ridiculous BS, Richard. Why don't you just bow out of this thread if that's the best you have to offer.

I didn't pay his post any attention. There are several on here you just have to look over as they don't exist.

 

[jsthntn247]

Agreed, it sounds like jsthntn247 is following the commonly prescribed fundamentals, does not seem to be anything wrong with his process.

jsthntn247, the only thing that seems a bit odd is your headspace measurements. I also use mitutoyo calipers + hornady gauge and my 223 cases measure around 1.460 fired. Are yours really 1.260? If so, perhaps we are using different inserts with the hornady comparator. I am using the one that says 'A330'.

Try measuring a few of your cases in several places before and after resizing to see how much you are working the brass. You can lightly scratch a mark on the outside. Using a marker, the marks may come off when resizing with lube.

View attachment 1021381

I marked a fired case as described and also marked a new case in the same spots and took measurements. Headspace measures 1.460 not 1.260 when fired and 1.458 sized.

 

[Ned Ludd]

I didn't pay his post any attention. There are several on here you just have to look over as they don't exist.

Brad - I get that, but I simply don't care for that kind of behavior, it's arrogant, rude, and completely unnecessary.

Back to your topic - below are my notes from 3 brass preps for the original .223. They consist of the initial virgin brass prep, then the preps after the first two firings. I set the Redding FL resizing die to knock the shoulder back about .002". In the initial prep, I first used the oversized expander mandrel to open up all of the virgin necks to a minimum diameter larger than the resizing die bushing (0.248"), then resized the necks back down with the FL bushing die. This really doesn't do much with the shoulders on virgin brass. The next two preps on fired brass push the shoulder back approximately .002". Each data set is composed of 10 cases selected at random, then measured before/after the resizing process so you can directly see the change for each case. The average values for all 10 case measurements +/- SD are boxed at the bottom of each page.

Brass Prep #1 (virgin)

Brass Prep #2 (1X-fired)

Brass Prep #3 (2X-fired)

These should give you something with which to compare your case measurements. As others have mentioned, I'm concerned about your getting CBTS (cartridge base to shoulder) measurements in the 1.25"-1.26" on virgin brass. The measurement with virgin brass straight out of the box should be somewhere in the 1.442" range. I'm hoping that your 1.25"/1.26" measurement is somehow a typo or misreading with the caliper tool. If not, that's likely your problem right there. In my hands with 3 different .223s, Lapua brass grows at the shoulder by .008" to .009" on the first firing. After that, I knock it back by about .002" every firing and I've never had any casehead separation issues. The primer pockets give up long before any casehead separation. If you're somehow getting brass with CBTS measurement that short, it's either a messed up Lot, or you did something in the initial (and subsequent) preps to push the shoulder back like 0.19". I'm not even sure how you could do that, which is why I'm hoping your CBTS measurements were typos and that you really meant 1.45" instead of 1.25". There's simply no way the CBTS measurements should be that short. If they are, and your chamber was cut properly, then your cases will be growing by close to 0.19" on the first firing. If that is the case, I'm shocked the casehead didn't separate on the very first firing. It's ok to move the shoulder .008" to .009" on the first firing, as long as you only set it back about .001" to .002" on all subsequent firings. Otherwise, you're stretching the hell out of the brass at the weakest point, which is right above where the webbing/casehead thins out into the standard wall thickness of the upper part of the case. It can take a few thousandths the first time, but if the shoulder is continually bumped back more than .004" to .005", it won't take that for very long at all.

Can you describe your brass prep process in exact detail, starting with how you prep virgin brass out of the box, then continuing through your subsequent fireformed brass prep process? I think if you can go through it in detail and provide your CBTS measurements at each step, it may make it easier for others here to help you troubleshoot and pinpoint the exact point of the problem. If the CBTS measurement you're giving are correct, something is either wrong with the brass straight out of the box, or else your chamber is not cut correctly. I'm hoping it's a only measurement discrepancy, but if not, that's most likely the root cause of the casehead separation.

Edited to add: I see you corrected your measurement values while I was typing this. Still, describing your process step by step from virgin to fireformed, along with measurements at each step will likely help you pinpoint where in the process the problem is occuring. At this point I can't tell you the specific underlying cause/step, but I am pretty certain the general mechanism involves too much shoulder movement at some point in your process, which results in the brass weakening and failing in that specific region. Step by step measurements should reveal where/when the problem occurs.

 

[Sheldon N]

I marked a fired case as described and also marked a new case in the same spots and took measurements. Headspace measures 1.460 not 1.260 when fired and 1.458 sized.

Just tossing out ideas here, but looking at your measurements you've got a fair amount of taper in your sizing die vs your chamber. Perhaps that contributes to the effect of base of the case gripping the chamber wall early in the firing process then more movement of the body/shoulder with associated stretch. Not sure if that's even a thing, just brainstorming.

Also didn't see this clarified earlier. How hot are the loads you're shooting?

 

[jsthntn247]

Just tossing out ideas here, but looking at your measurements you've got a fair amount of taper in your sizing die vs your chamber. Perhaps that contributes to the effect of base of the case gripping the chamber wall early in the firing process then more movement of the body/shoulder with associated stretch. Not sure if that's even a thing, just brainstorming.

Also didn't see this clarified earlier. How hot are the loads you're shooting?

This is my FTR rifle with 90 vlds at 2850. Its throated out a mile also and quckloads predicts 55k on the pressure. This is a very common load and allot of others are using it with no case failure issues, primer pockets go waaay before any other issues, but I have primer pockets still tight with cracked cases. When I took those measurements I thought the same thing as you, seems is sizing allot more at the top than the bottom which should cause it to grow more than usual.

 

[jsthntn247]

Brad - I get that, but I simply don't care for that kind of behavior, it's arrogant, rude, and completely unnecessary.

Back to your topic - below are my notes from 3 brass preps for the original .223. They consist of the initial virgin brass prep, then the preps after the first two firings. I set the Redding FL resizing die to knock the shoulder back about .002". In the initial prep, I first used the oversized expander mandrel to open up all of the virgin necks to a minimum diameter larger than the resizing die bushing (0.248"), then resized the necks back down with the FL bushing die. This really doesn't do much with the shoulders on virgin brass. The next two preps on fired brass push the shoulder back approximately .002". Each data set is composed of 10 cases selected at random, then measured before/after the resizing process so you can directly see the change for each case. The average values for all 10 case measurements +/- SD are boxed at the bottom of each page.

Brass Prep #1 (virgin)

Brass Prep #2 (1X-fired)

Brass Prep #3 (2X-fired)

These should give you something with which to compare your case measurements. As others have mentioned, I'm concerned about your getting CBTS (cartridge base to shoulder) measurements in the 1.25"-1.26" on virgin brass. The measurement with virgin brass straight out of the box should be somewhere in the 1.442" range. I'm hoping that your 1.25"/1.26" measurement is somehow a typo or misreading with the caliper tool. If not, that's likely your problem right there. In my hands with 3 different .223s, Lapua brass grows at the shoulder by .008" to .009" on the first firing. After that, I knock it back by about .002" every firing and I've never had any casehead separation issues. The primer pockets give up long before any casehead separation. If you're somehow getting brass with CBTS measurement that short, it's either a messed up Lot, or you did something in the initial (and subsequent) preps to push the shoulder back like 0.19". I'm not even sure how you could do that, which is why I'm hoping your CBTS measurements were typos and that you really meant 1.45" instead of 1.25". There's simply no way the CBTS measurements should be that short. If they are, and your chamber was cut properly, then your cases will be growing by close to 0.19" on the first firing. If that is the case, I'm shocked the casehead didn't separate on the very first firing. It's ok to move the shoulder .008" to .009" on the first firing, as long as you only set it back about .001" to .002" on all subsequent firings. Otherwise, you're stretching the hell out of the brass at the weakest point, which is right above where the webbing/casehead thins out into the standard wall thickness of the upper part of the case. It can take a few thousandths the first time, but if the shoulder is continually bumped back more than .004" to .005", it won't take that for very long at all.

Can you describe your brass prep process in exact detail, starting with how you prep virgin brass out of the box, then continuing through your subsequent fireformed brass prep process? I think if you can go through it in detail and provide your CBTS measurements at each step, it may make it easier for others here to help you troubleshoot and pinpoint the exact point of the problem. If the CBTS measurement you're giving are correct, something is either wrong with the brass straight out of the box, or else your chamber is not cut correctly. I'm hoping it's a only measurement discrepancy, but if not, that's most likely the root cause of the casehead separation.

Edited to add: I see you corrected your measurement values while I was typing this. Still, describing your process step by step from virgin to fireformed, along with measurements at each step will likely help you pinpoint where in the process the problem is occuring. At this point I can't tell you the specific underlying cause/step, but I am pretty certain the general mechanism involves too much shoulder movement at some point in your process, which results in the brass weakening and failing in that specific region. Step by step measurements should reveal where/when the problem occurs.

I expand new brass on a mandrel and shoot it. I just measured some new unfired brass and it measured 1.455-1.458 and my headspace is 1.460 on 2x fired brass. After the first firing brass will vary from 1.457-1.460. I take a couple longer 1.460 cases and set the die to bump them to 1.458 because I know from measuring my chamber that this is the longest number on "my tool" that will allow the bolt handle to drop freely with no drag on the shoulder from the chamber. Some of the cases that are 1.457 after the first firing will actually grow 1/2 thou after sizing but they do not bump back. After the second firing and all subsequent firings all cases measure 1.460 and I bump to 1.458. I check and re check the first 10 or so cases when setting the die up to resize so I am sure of my number then check 1 out of every 10 during the process. That's why I can't figure out what's going on. As I've discussed with you I'm now firing two light loads in brass before a full powered load trying to harden the cases and extend primer pocket life but if I can't figure this issue out it's not going to matter.

 

[Jdne5b]

Maybe you got a bad lot of brass? Has this happened to different lots?

Is this chamber from your own personal reamer? Might be worth a custom Whidden sizing die if you're going to keep that reamer for a while.

 

[jsthntn247]

Maybe you got a bad lot of brass? Has this happened to different lots?

Don't know, I just started on a new lot.

 

[JFM33]

Don't know, I just started on a new lot.

The gap between the bolt face and the barrel is probably out of spec.I have seen it befor.That is why I asked about those measurements.
If you know the headspace is right and you are not bumping the shoulder back to far the next place I would look is how much of the case rim is unsupported.

 

[Dos XX]

The gap between the bolt face and the barrel is probably out of spec.I have seen it befor.That is why I asked about those measurements.
If you know the headspace is right and you are not bumping the shoulder back to far the next place I would look is how much of the case rim is unsupported.

What is the cause of unsupported case rim? Is that a function of the barrel or the bolt? Is there a way to measure that easily? Would you measure the bottom of the case before firing and after and compare?

Brad,
Is this a new barrel or have you fired other lots of brass through this barrel? If new barrel, same reamer as previous barrels?

 

[JFM33]

What is the cause of unsupported case rim? Is that a function of the barrel or the bolt? Is there a way to measure that easily? Would you measure the bottom of the case before firing and after and compare?

Brad,
Is this a new barrel or have you fired other lots of brass through this barrel? If new barrel, same reamer as previous barrels?

If the barrel is off then you can incert a go gauge and measure from the end to the barrel face.Next measure from the bolt rim to the bolt face.
Subtract the bolt measurement and you are left with the unsupported number or barrel to bolt face gap .
I have also seen where the angle of the coned bolt doesn't match the barrel contour leaving an are unsupported.
He could incert the cases with the fail lines into the chamber for a reference to see if it is closer to the barrel face.

 

[JFM33]

JST you are right that the primer pockets will almost always go befor a case failure in the 223 if the case is supported.

 

[Ned Ludd]

JST you are right that the primer pockets will almost always go befor a case failure in the 223 if the case is supported.

Brad - have you checked the chamber with a borescope? It's possible there might be something out of whack. Otherwise, I'm at a loss to explain your problem, other than a bad Lot of brass. However, didn't you have this same issue with an earlier Lot of brass that you brought to the MO State Match? If there is too large of a gap between the bolt face and the base of the case, I would agree that you'd never see that by measuring CBTO with a Hornady OAL gauge. However, you will still see it show up because the fired cases would be growing more than you'd expect on the first firing, but then be fine after that if you specifically bump the shoulder back only .001" to .002". In other words, they'd still lengthen out during the firing process to the boltface length dimension, even if it was out of spec. It seems as though somehow the brass is being overstretched on the first firing, even if your measurements don't support that idea, leading to casehead separation even though you're bumping the shoulders an appropriate amount after the first firing. I'm afraid it's beyond my skill level to diagnose on the internet. Have you spoken with your smith about it?

 

[BoydAllen]

I just trashed a couple hundred Lapua 223 cases after 4 firings. I had one separate on me which got me to looking at the rest of them. Some had no signs, some had light discolored lines near the case heads but not detectable cracks, and some had cracks you could feel with your fingernail. I use a redding type S die and have measured my shoulders when FL resizing to only bump 2-3k when sizing. I recently checked my comparator with the method of removing the firing pin assembly and chambering, sizing, chambering, sizing until no resistance is felt from the case and the numbers match what I have been bumping back to within .001, so it's not an over bumping shoulder issue. Could it be that my die is squeezing the cases too small in diameter near the datum line and causing this issue or something else? This is my ftr rifle chambered with a PTG match reamer.

Any chance that you annealed these cases?

 

[jsthntn247]

What is the cause of unsupported case rim? Is that a function of the barrel or the bolt? Is there a way to measure that easily? Would you measure the bottom of the case before firing and after and compare?

Brad,
Is this a new barrel or have you fired other lots of brass through this barrel? If new barrel, same reamer as previous barrels?

First lot of brass through this barrel, has 1300 rounds on it now. Same reamer as last barrel

 

[jsthntn247]

If the barrel is off then you can incert a go gauge and measure from the end to the barrel face.Next measure from the bolt rim to the bolt face.
Subtract the bolt measurement and you are left with the unsupported number or barrel to bolt face gap .
I have also seen where the angle of the coned bolt doesn't match the barrel contour leaving an are unsupported.
He could incert the cases with the fail lines into the chamber for a reference to see if it is closer to the barrel face.

So how would excessive clearance lead to case head separation?

If the barrel is off then you can incert a go gauge and measure from the end to the barrel face.Next measure from the bolt rim to the bolt face.
Subtract the bolt measurement and you are left with the unsupported number or barrel to bolt face gap .
I have also seen where the angle of the coned bolt doesn't match the barrel contour leaving an are unsupported.
He could incert the cases with the fail lines into the chamber for a reference to see if it is closer to the barrel face.

There is .135 of unsupported case sticking out from the end of the chamber.