Case head separation

[JB.IC]

Quick question,
Would a 0.018” difference in headspace cause a case head separation?

Had some expensive ass brass separate on the first firing. The virgin brass shoulder is 0.018” smaller than some once fired brass of another manufacturer.

Chamber job was done by a professional ELR gunsmith and Peterson brass has zero issues with said chamber. Virgin Peterson brass is about 0.007” smaller than once fired Peterson brass. (For reference)

not naming the manufacturer in question until I personally speak with them about the issue.

 

[Supersubes]

A new piece of brass taking its first ride should survive that. In other words, they shouldn’t separate on the first firing. It’s not good though, but there can be several causes. The separations usually occur when you size the case back down near the virgin length and fire it a few more times. Did yours occur on the first firing?

Some cartridges are very short in virgin form. Lapua brand 338 LM and Peterson 300 Norma are examples of this. So the gunsmith can cut an in spec chamber that passes the go/no-go test, and you see a bunch of growth on the first firing because the brass is so short. I’d suggest you first determine using gauges if your chamber is in spec.

 

[Steel head]

A new piece of brass taking its first ride should survive that. In other words, they shouldn’t separate on the first firing. It’s not good though, but there can be several causes. The separations usually occur when you size the case back down near the virgin length and fire it a few more times. Did yours occur on the first firing?

Some cartridges are very short in virgin form. Lapua brand 338 LM and Peterson 300 Norma are examples of this. So the gunsmith can cut an in spec chamber that passes the go/no-go test, and you see a bunch of growth on the first firing because the brass is so short. I’d suggest you first determine using gauges if your chamber is in spec.

this.

 

[LawnMM]

I'm also assuming this is multiple firings. The answer to your question is yes, over time.

If you blow them out 0.018 on the first firing and only bump 0.002-0.003 thereafter I would not expect problems.

If you're going back to zero and bumping/blowing out that much every cycle I'd be surprised if you made it much past 5 firings.

 

[JB.IC]

Brass is virgin and separating on the first firing. Sorry I thought I made that clear but I didn’t.

 

[Milo 2.5]

Quick question,
Would a 0.018” difference in headspace cause a case head separation?

Had some expensive ass brass separate on the first firing. The virgin brass shoulder is 0.018” smaller than some once fired brass of another manufacturer.

Chamber job was done by a professional ELR gunsmith and Peterson brass has zero issues with said chamber. Virgin Peterson brass is about 0.007” smaller than once fired Peterson brass. (For reference)

not naming the manufacturer in question until I personally speak with them about the issue.

It seems as though you have answered your own question. Apparently it is, if your Peterson is growing 7 thou, and it is fine, but brand x is growing 18 thou and not surviving, it is too much growth for that brass.
Either jam your bullets for the first firing, or make a false shoulder if you are determined to run this brass. I would also take a measurement of the diameter of the brass where it is coming apart, compare to unfired brass, because a double whami both in length and outward movement can really stress brass.

 

[JB.IC]

It seems as though you have answered your own question. Apparently it is, if your Peterson is growing 7 thou, and it is fine, but brand x is growing 18 thou and not surviving, it is too much growth for that brass.
Either jam your bullets for the first firing, or make a false shoulder if you are determined to run this brass. I would also take a measurement of the diameter of the brass where it is coming apart, compare to unfired brass, because a double whami both in length and outward movement can really stress brass.

this is the answer to the question I didn’t formulate properly. Thanks.

 

[Milo 2.5]

this is the answer to the question I didn’t formulate properly. Thanks.

It may have helped if you said what case you are shooting. A 375 cheytac growing 18 thou not nearly as catastrophic as some skinny 6mm case. And with the smaller case, the probability of misfires rises with that amount of headspace or growth.

 

[JB.IC]

It may have helped if you said what case you are shooting. A 375 cheytac growing 18 thou not nearly as catastrophic as some skinny 6mm case. And with the smaller case, the probability of misfires rises with that amount of headspace or growth.

it’s a cheytac based cartridge.

the area where it separated was only a growth difference of 0.010” between 1x fired and virgin.

for the Peterson it was only a 0.007” growth between virgin and 1x fired at the area it would hypothetically separated at. I’m using Peterson as reference because I’ve had no issues with this brass and I can actually measure the brass considering it’s in one piece.

 

[lightman]

A head separation on the first firing sounds extreme. I would check the headspace of your chamber, just to rule that out as a problem. Not pointing the finger at your gunsmith but everyone makes mistakes, even the best.

My next thought is that you got a bad batch of brass. Its either the brass or the chamber. Have you modified your dies? What brand of dies are you using? What caliber is this?

 

[Milo 2.5]

it’s a cheytac based cartridge.

the area where it separated was only a growth difference of 0.010” between 1x fired and virgin.

for the Peterson it was only a 0.007” growth between virgin and 1x fired at the area it would hypothetically separated at. I’m using Peterson as reference because I’ve had no issues with this brass and I can actually measure the brass considering it’s in one piece.

I know you said you did not want to call out the brass maker, and I honor that. But if you are talking about Bertram brass, google may be your friend here, because you are no pioneer if that is the case here.

 

[JB.IC]

I know you said you did not want to call out the brass maker, and I honor that. But if you are talking about Bertram brass, google may be your friend here, because you are no pioneer if that is the case here.

I wish it was them. Then I’d look less of an idiot lol. I want to give the owner a chance to correct before I inform anyone. Plus I want to try the 0.010” lands jam and see if that fixes the issue. Although I shouldn’t have to do that.

 

[supercorndogs]

I would be worried about brass that was separating from .018 of growth. That is about normal for what I have seen on 300wm brass.