Help with fire forming a wildcat

[Brians356]

brian356, I didn't ignore your suggestion to measure and compare. Ive been at work since 6am and just got home hour ago. the necks are longer on the bertram brass ONLY after fire forming. Before fire forming the brass are 2.090" after forming the Bertram brass comes out to 2.095 to 2.100". I think you might be right about the brass being undersize. Ill check tomorrow and get back. Thats the only thing that makes sense right now

An approach to comparing body diameters of virgin cases: Measure, say, approximately 0.2" from the base up the body of a Winchester case, and make a mark there with a sharpie. Clamp the caliper on the body at the mark, and lock it at that setting (ignore the measured diameter.) Now move the caliper, still locked, to a virgin Bertram case, sliding it down from the shoulder towards the base until it wedges, and mark where it stops with the sharpie. A very slight difference in body diameter will change the mark's distance from base noticeably compared to the Winchester case.
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[Bigd7378]

brian356, I just did this. The Bertram brass has a larger diameter than the Winchester. the sharpie mark was noticeably higher on the case body of the Bertram than on the Winchester case. I tried with multiple case of each brand all new and unfired. Winchester was by far the smallest followed by Hornady,Bertram and Norma being the largest. I also measured three cases from each brand just above the extractor groove and .220" up from the bottom of the rim.
Here is a picture of a Bertram on left vs Winchester with the sharpie method.
And also a picture of the measurements I Miked on the cases, average of three

I have a 6.5-06 ackley Imp, and a 223AI and I use the same fire forming techniques. and never have issues.
Im baffled what's going on with this. I really would like to use the Bertram because it seems very consistent on case weight and measurements. I know a lot of people complain about Bertram being inconstant but my 100 cases are way better than Win, Hornady and on par with Norma, Maybe I just got a decent batch. Also the bertram is the lighest by far with the most water capacity by quite a bit.

Im beginning to wonder if the cases are just to hard and need to be annealed before fire forming
thoughts??

 

[spclark]

Also the bertram is the lighest by far with the most water capacity by quite a bit.

That would lead me to believe those case walls are thinnest of any of the brands you've mentioned, which may very well be an indicator for what you're seeing.

Can you section a new, unfired case? Compare case wall thickness as the wall thins towards the shoulder?

When I started noticing incipient separations with the Palma brass I'd formed up for 284INCH, and with Jameson 25REM I'd formed for 6HAGAR, case walls thinned above the case web at a consistent spot (different for each case style but consistent among brands) which is exactly where the stretch marks eventually showed up.

 

[Burnt Powder]

What action, what kind if ejector?
I’m sure I’ll get roasted for this comment, but so be it!
I’ve got a 6 Rem AI that is very unique, I’ll not go into that, but I’ve had some similar difficulties forming brass with it too. As a last resort I sprayed a light coating of ZEP 45 penetrating-lube on the loaded cartridge before chambering. Bang! Out pops perfectly formed brass with no sign of any stretch or head separation! Just saying what cured my issue. I’ve formed several hundred cases like that. Doubt I’ll ever have to do anymore before it goes to one of the kids or grandkids.

 

[wedgy]

I just got thru putting a false
shoulder on 200 cases of RWS 270 brass to form for a 6.5 Sherman. I necked up to .284" and then partially sized the neck enough to close bolt under med. heavy pressure.

I've used this method for 10 years or so, to not have to deal with COW. Been a big improvement.

It's pretty simple, if you use a generic neck sizer or a bushing die. Just be sure your parent case length is not longer than your forming chamber OAL.

View attachment 1166034

Willie, can you explain the purpose of necking the .270 up to .284 first ? Then you partially size to 6.5 leaving some expanded to create pressure to form the case ??
Also, I was thinking of a 6.5 Sherman to push the Berger 156, what bullets have you had luck with ?

 

[Brians356]

What action, what kind if ejector?
I’m sure I’ll get roasted for this comment, but so be it!
I’ve got a 6 Rem AI that is very unique, I’ll not go into that, but I’ve had some similar difficulties forming brass with it too. As a last resort I sprayed a light coating of ZEP 45 penetrating-lube on the loaded cartridge before chambering. Bang! Out pops perfectly formed brass with no sign of any stretch or head separation! Just saying what cured my issue. I’ve formed several hundred cases like that. Doubt I’ll ever have to do anymore before it goes to one of the kids or grandkids.

I wet my 22-250 case bodies with Rem Oil or Kroil when fireforming to 250 AI bulletless and it works to minimize stretching at the web and also promotes full formed, sharp shoulders (with adequate powder charge of course).
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[Brians356]

Also the bertram is the lighest by far with the most water capacity by quite a bit.

How much lighter, and how much more capacity? Especially compared to Norma, as I notice the Norma seems to have similar diameter as you measured.

Have you compared case lengths from base to shoulder datum, using a Hornady "headspace" tool? I'm wondering if the Bertram case has extra headspace (i.e. shoulder is set back too far). Your false shoulder notwithstanding, that could cause stretching.
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[Bigd7378]

weight of the virgin 300 WSM brass is as noted below. weights are average of 10 random cases per 100
empty with primer---------- water capacity to top of neck
Bertram 215.5 gr ---- 88.0 gr
Winchester 233.5 gr ---- 85.5 gr
Hornady 240.0 gr ---- 85.0 gr
Norma 258.0 gr ---- 83.0 gr

 

[Bigd7378]

I'm beginning to think the Bertram is just too thin. I really wanted to use this brass because of the hardness and case capacity it has. My lot has been very consistent on weight and measurements. But I guess its time to go back to Winchester

 

[Brians356]

weight of the virgin 300 WSM brass is as noted below. weights are average of 10 random cases per 100
empty with primer---------- water capacity to top of neck
Bertram 215.5 gr ---- 88.0 gr
Winchester 233.5 gr ---- 85.5 gr
Hornady 240.0 gr ---- 85.0 gr
Norma 258.0 gr ---- 83.0 gr

Wow. Concentrating just on Bertram vs Norma (which had similar outside diameter) that's a 6% larger capacity for Bertram, and Norma 20% heavier case than Bertram! The Bertram case walls must be awfully thin.

Are all these cases trimmed to the same OAL before measuring capacity?

You mentioned Bertram has a "longer neck". What does that mean exactly? (There's two ways to interpret the statement.)
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[Willie]

Willie, can you explain the purpose of necking the .270 up to .284 first ? Then you partially size to 6.5 leaving some expanded to create pressure to form the case ??
Also, I was thinking of a 6.5 Sherman to push the Berger 156, what bullets have you had luck with ?

The false shoulder holds the case against the bolt face for forming without excessive stretch.

I'm running the 156 now @ 3120 with Retumbo with Norma 280 brass. I'm hoping to exceed that with the RWS 270 brass. When sized to 6.5, neck thickness is .0145" and gives me .004" clearance in the .297" chamber.

 

[Brians356]

I'm beginning to think the Bertram is just too thin. I really wanted to use this brass because of the hardness and case capacity it has. My lot has been very consistent on weight and measurements. But I guess its time to go back to Winchester

Someone mentioned sectioning a Bertram case (longitudinally) for inspection. But an easier alternative is to simply saw it across the body a half inch or so above the base, and measure the case wall thickness using a ball (tubing) micrometer (and compare to a Norma cut the same length.) You just have to measure both cases the same distance from the base as the walls are tapered. (A proxy is to just compare the neck wall thicknesses, but that's a bit too much of an extrapolation for my curiosity.)
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[Bigd7378]

yes they were all trimmed to 2.090" I guess I need to clarify the neck length issue. Yes they are all the same
After fire forming the Bertram brass grows to 2.095" to 2.100" Only the Bertram gets longer. Its noticeable by just looking at them compared to the other brass. So yes these are stretching

 

[Bigd7378]

brian356 I did that exact thing.I cut them in half and measured them earlier today
Bertram .0334"
Winchester .0372"
So Bertram is .0038" case wall thinner than winchester

 

[spclark]

So Bertram is .0038" case wall thinner than winchester

BINGO...

You might still be able to use it BUT you’ll need to 1) form a well-defined false shoulder the first time you prep cases then 2) use fairly weak loads (COW or bulleted, being respectful of the difference!) more than once to get cases that just don’t put much forward / backward force into those thin walls.

 

[Brians356]

BINGO...

But at least it seals off the chamber readily.
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