Fire forming with bullet

[Madchase]

I’ve been studying case head separation a little bit. What I’m wondering is if incorrect head space can contribute to case head separation, how come fire forming brass with a bullet doesn’t contribute to case head separation? Never had a case head separation happen to me but when you read about it, incorrect brass forming is the reason. When fire forming hardly anything inside the camber has correct measurements.

 

[JFrank]

I’ve never seen case head separation from fire forming, on the other hand I have experienced case head separation as a result of repeated over working of the brass during the resizing phase.

 

[SKWERLZ]

Excessive case stretch can do it.
300 and 338 Norma brass is often really short in standard chambers that pass a go gauge and not the no go.
Great candidate for a false shoulder.
I seem to get a lot better results with false shoulders than with jamming the bullet.

 

[Coyotefurharvester]

Because proper fire forming is minimizing brass stretch(false shoulder, bullet seated into lands) while allowing brass to expand(shoulder angle, shoulder dia, etc.) to fit chamber. After that minimal sizing is required.

 

[spudgun]

Excessive headspace will also cause case separation.

The first signs are a bright shinney ring at the top of the web.

 

[6.5 forever]

I’ve never seen case head separation from fire forming, on the other hand I have experienced case head separation as a result of repeated over working of the brass during the resizing phase.

Correct. Repeated over sizing is the cause of head separation. Once the case is chamber formed you should try to minimally resize it

 

[L.Sherm]

To me it depends on how I fireform depending on cartridge, with an AI and new brass I go past touch atleast .010 with atleast .004 nk tension.
If I'm not wrong an AI chamber should have .004 crush so there shouldn't be any headspace issues but I go past touch anyway.
On new brass thats short I just knock the load back 1.5-.2.0 grains and go past touch for the first firing.
With something like a Dasher false shoulder.

 

[linebaugh]

If dies are not set for incorrect headspace and run as though the chamber is normal, setting shoulder back to sammi repeatedly and not knowing it would probably cause this at so e point.

 

[swd]

I’ve fire formed 600-800 6 BRX cases over the years. The shoulder is blown .100” forward. Heavy neck tension with the bullet hard jammed and I’ve never had a case head failure.

 

[NCVarhtr]

I’ve fire formed 600-800 6 BRX cases over the years. The shoulder is blown .100” forward. Heavy neck tension with the bullet hard jammed and I’ve never had a case head failure.

Thats the best way to prevent case head separation.

 

[swd]

I should also mention if it has a plunger ejector take out and use a soft primer like Winchester. And they shoot incredibly well during fire forming. I fire form at 600 yard match’s and the rifle will shoot X’s like crazy.

 

[209jones]

I've always wondered a bit on how the initial stretch in fireforming affects case life. it would seem that it's not all that bad, depending on the chamber you start it off in, and how you size it after that intial stretch, along with how hot of a load you put in it after that initial stretch. Sure there have been cases of short CBTD and a big chamber around, that sort of thing happens, seems to me Enfields are prone to that..

 

[AlNyhus]

A bit of light lube on the cases when fireforming minimizes case stretching and helps the case comform to the chamber.

Good shootin' -Al