First case head separation

[Carey Farmer]

I have a question about this, "Whenever I full-length size, the squeeze of the case body causes the case to lengthen by about 0.002". If I don't bump the shoulders at all after the first firing, the cases chamber is a little snug in my short-headspace chamber. So I bump the shoulders back to the same headspace they came out of the chamber. I continue to do this on subsequent firings. Haven't seen a need to bump the shoulders shorter than they came out of the chamber."

Am I to assume that you partially full-length size, then bump the shoulder back with a separate die in a second operation, or does a partial full-length size to the shoulder length of the fire-formed case suffice since you took .004 off the bottom of the die?

Thank you for your kind words, sir. I'm not qualified to teach, but am happy to explain the approach that seems to work for me.

My kids, my brother, and I all have rifles in the same chamberings, and I load for everyone in my family, so I can't just set my full-length sizing die base-to-shoulder-length adjustment collar / locking ring and forget it. Every time I'm loading for a particular rifle, I have to "find" the shoulder of a representative fired case.

I find the case shoulders by backing out the sizing die a few thousandths, and then repeatedly sizing the same (representative) case, measuring the case length and then screwing the sizing die in to the collar a thousandths or so after each sizing, until I feel some additional resistance in the press handle, or see a reduction in case length. As mentioned in my previous post, the case gets longer before it gets shorter.

After I see the die has contacted the case shoulders, I try to screw the sizing die in just a half a thousandth or so at a time, until the sized case length is the same as the fired but unsized case length. Then I use that collar setting for the whole batch of fired cases.

All the rifles I load for are within a few thousandths of the same headspace, so there's not a whole lot of trial and error in this process. But screwing in a thousandths is a very small adjustment, only about 1/32" movement of the collar, so it's pretty easy to overshoot.

I do re-lube the representative case every time I size it. And I don't use an expander ball, to prevent excess working of the case neck with the repeated sizing.

 

[dwsitz]

I did this with 300 Sherman once, no belt.

Action type seems to have some impact….I.e. axial flex Also, I hypothesize that the hardness gradient from base to shoulder area of new brass affects how it forms to the actual chamber quite a bit.

In my first round of 300 Sherman, I fireformed with an ~ 50000psi load. Slow, but firm. The 280ai brass seemed stronger in the shoulder than the case body. Even with a false neck, the cases stretched and after 4-5 firings showed a thin spot towards the base.

The next time I used 270 Starline brass and the COW method. I'm at around 3-4 firings now with no thinning. I think if I were using magnum brass, I would anneal shoulders to encourage that area to form when COW forming.

I annealed 270 brass about 1/3 rd the way down the case to form 25-06 AI brass.took some sizing and trimming but got my lost .020 length back. I used Nosler 280 brass as well,the shoulder was bumped a tad,loaded and fired,no trimming needed. I would like to try the cow method,although I'm not sure I'll go back with 270 brass.

 

[Mike Matteson]

Headspacing belted cases on the belt could potentially separate any brass no matter what brand.

Tool? You mean a bent paper-clip, there's no need for that, just have a look at the case on right, there's imminent separation, possibly within 2 firing.

I had that problem a long time ago. I changed to neck sizing my case with belted mag cases. That ended the problem. After than is was primer pockets that ended the case use. I was shooting a 308 NM. It's shorter to the shoulder than the 300WM. the neck is longer. At the time I couldn't get my hands onto a neck sizing die for the 308 NM case. So tried a 300WM neck sizing die. It only sized about about 2/3 or so of the necks. The balance of the neck remained fired form to my 308 NM chamber. It's been a long time that I have reloaded for that rifle. I can't remember if I had chambering trouble after the cases was fire form the case. It seem like I didn't have any problems. By changing my reloading practice it improved my groups. Some but I was in the 1/2 range @ 100yds at that time with that rifle. That was over 20 years ago. It was done on RCBS dies. Nothing fances either.
I have been without a reloading place for almost 2 yrs now. I believe I am findly going to get it build in the next two weeks of so. To many other project I get involve with. Got to Stop that!
Bottom line it's a learing curve here.

 

[snox801]

I'm actually shocked it didn't lose the primer pockets first. That seems to be what always gives up on my .257

 

[VarmintBob]

The bent paper clip will find cases which will split on the next firing regardless of whether or not you can see any indication on the outside of the case. Any case fired 6 times or more gets the paper clip test before it goes in a save for resizing bag. I find case head separation a more commone end of case life indicator than primer pockets being too big. I use the most oversized primers I know of.