First case head separation

[Rich Coyle]

Magnum, I disagree. No disrespect intended. Whenever I size cases, I have calipers in hand. I check every case for correct headspace at 0 to -.001". If I don't check with that paper clip tool that I ground to a sharp edge, I get head separation.

When I can afford it I will have the chamber redone to actual 40° and get some new dies. I heard that will solve the problem.

 

[MagnumManiac]

Rich, you may disagree, but my pic above proves that case does not stretch on the first firing at the web, nor does it after being fired with neck sizing only for 3 firings and THEN measured and bumped .0015" for 10 firings…no stretching occurs.
Case design has nothing to do with case stretching, what does is what the handloader does to it.
Anyway, I will just keep quiet on this subject from now on…

 

[1mechanic]

Rich, you may disagree, but my pic above proves that case does not stretch on the first firing at the web, nor does it after being fired with neck sizing only for 3 firings and THEN measured and bumped .0015" for 10 firings…no stretching occurs.
Case design has nothing to do with case stretching, what does is what the handloader does to it.
Anyway, I will just keep quiet on this subject from now on…

The chamber in your rifle maybe tight and in turn reduce any case stretching. A chamber that is cut long and depending on the brass can have flow and thinning of the brass above the belt after the first firing.

 

[dnb86]

one mistake I made when I was green (not saying anyone in here is ) was bumping shoulders after the first firing and my measurements were off do to the fact that brass needs at least 3-4 firings before bumping shoulders ( in my opinion ) do to that fact that the brass is still stretching on it's own just from the firing. So my next lot of brass I fired off one round measured it and loaded that same brass 3 more times only neck Sizing and that brass grew 6 thousands more before it stopped growing. So if I were to measure the shoulders after the first firing and bumped 2 thou back I was bumping about 8-10 thousands off its true maximum growth and that was just in my chamber so some chambers will let brass grow longer than others as well

 

[nksmfamjp]

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.

 

[VarmintBob]

Cases stretch every time you fire them. The cables holding up the golden gate bridge stretch when a sparrow lands on the road. It's all just a matter of degree. If you can fire any case enough times it will split on the body somewhere due to this stretching. High pressure and exaggerated body taper cause more stretching. Some cases split near the base. Some (like 223 Rem) split further up. If you bump the shoulder back more than a couple thou when resizing the splits happen earlier in the case life cycle. I've had cases split at 4 firings when doing everything right. I have a friend with ADG 22 GT brass that has made it through 19 firings.

 

[VinceMule]

The Term, "Size to Fit The Chamer" is a shore enough can of worms. Headspace length is one issue, dia of the reamer used, dia of the Chamber, and dia of the die sizes to at the web is of critical importance.

Also, some gunsmiths use techniques that cut to reamer size while some do not.

Factory chambers are usually generous in web dimensions, set some of the brass to headspace length in these chambers and you still will not be able to close the bolt easily due the web dia not being reduced enough, dies can vary greatly, not to mention brass spring back.

If you take a 7 mag and reduce the pressure to where you can neck size for 5 firings, you may as well be shooting a 24" 280 Remington where you can shoot the 160g at 2930 with IMR 7828, Federal 210, a load right out of the Nosler Manual #3, not meant for pumps and semi-autos.

Practically ALL F-class shooters and Benchrest shooters are full-length sizing at this time due to accuracy nodes at the top end of the pressure curve.

Today, custom reamers are being made by gunsmiths to get rid of the "bolt click" due to a mis match between PRS brass and current Production die dimensions. The custom gunsmiths are ordering reamers that are larger in the web.

This is redundant, but worth saying: Shooters are slowly catching on to the two dimensions that are critical on a chamber:

A. Headspace length

B. Web dia

European brass complicates all of this mess as European CIP standards produce larger web dia brass that often do not match SAAMI chambers nor SAAMI spec production Dies.

Magnum is EXACTLY right in that case head separations are due to the reloader pushing the shoulder back too far, but everyone can afford a $450 set of dies that match to the chamber reamer used or custom-designed off of fire-formed brass! Those of us who have to use production dies have to live with just throwing brass away as needed due to pushing the shoulder back too far to reduce the web dia.

We are all on a learning curve, and hopefully, we never quit learning, especially me.

 

[Philward]

Is 3200fps typical from a 257B firing a 133 grain bullet? I didn't read any load data posted...maybe missed it.

 

[RockyMtnMT]

I full length size everything. Just as @VinceMule said, it is the most consistent process time in and time out. I shoot stout enough loads that I lose primer pockets before I work brass enough to separate case head. 3-4 firings is good life in my opinion. Wildcat cartridges with lots of work to form I am more protective of but they also have custom dies that match that chamber. I still full length size but with less work on the brass, so it lasts longer.

 

[Carey Farmer]

Cases stretch every time you fire them.

Exactly. And belted cases typically stretch a LOT on the first firing. I can't help but think that sets up belted cases for case-head separation.

Almost every belted mag case I've bought has been around 0.015" short of a SAAMI chamber. So I had my belted mag reamer made up with headspace 0.010" short of SAAMI. Haven't found a brand of factory ammo that is too long to chamber. Only issue is I had to lap 0.004" off the bottom of my full length sizing die to be able to bump the shoulders of a fired case.

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 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.

I anneal after every firing. I aim my flame at the shoulder, not at the neck-shoulder junction, so I get a good anneal of the shoulders and upper case wall. When I anneal this way, it takes WAY less force on the press handle to bump the shoulders, so I'm pretty sure that I'm helping ensure that stretching in the chamber happens at the shoulder, not at the web.

With all of the above my belted cases have no problems with case head separation.

 

[Tulsa Reiner]

Is it headspaced on the shoulder or the belt?

It just occurred to me that I don't know how to head space based on the belt, or measure it. (It has been a long time since I loaded for my Weatherby rifles.) Can you describe it for me, anyone?

 

[VinceMule]

There is a lot to digest in Carey's post. Tulsa, Carey is probably speaking of two different things that got you confused, maybe. The bolt face to shoulder length is one issue, and the headspace on the belt is another issue. Carey is explaining what he does, and to some degree how he does it. His method is extremely advanced with custom tooling.

Carey's first line in his post is critical.

I hope that Carey chimes in and teaches more. He has already gone way out on a limb in posting his advanced processes, took a lot of courage!

Also, Carey's statement, "So I'm pretty sure that I'm helping ensure that stretching in the chamber happens at the shoulder, not at the web" is Noteworthy.

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?

 

[Hugnot]

I F/L size all my .300 WM brass. No head separations - I use a .006 feeler gauge between bottom of die & shell holder to prevent excessive case squashing. I always use the same shell holder that lives in the same box as the .300 WM F/L die.

Head space on shoulder. I never had a case separate on 1st firing. I try to buy cheap once fired brass.

A .002 length growth upon F/L sizing sounds reasonable. Using the .006 feeler gauge between shell holder & bottom of F/L die maintains head space at shoulder with successive sizing.

I ignore the belt, sort of useless with cases having moderate angle shoulders. Upon firing, pressure happens everywhere. I remember seeing gauges used for sizing belted cases, the idea being, sized brass should be flush with the top of gauge.

A .458 WM needs a belt. Seems like belted ammo is not intended for re-loading - shoot and toss. There are "long" belted cases available.

 

[Tulsa Reiner]

There is a lot to digest in Carey's post. Tulsa, Carey is probably speaking of two different things that got you confused, maybe. The bolt face to shoulder length is one issue, and the headspace on the belt is another issue. Carey is explaining what he does, and to some degree how he does it. His method is extremely advanced with custom tooling.

Carey's first line in his post is critical.

I hope that Carey chimes in and teaches more. He has already gone way out on a limb in posting his advanced processes, took a lot of courage!

Also, Carey's statement, "So I'm pretty sure that I'm helping ensure that stretching in the chamber happens at the shoulder, not at the web" is Noteworthy.

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?

I did what I would say was partial full length sizing, to get the neck resized. I've never had trouble with chambering my reloads for 257 or 300 Wby rifles. So I must have been resizing the body, but maybe not even moving the shoulder. That was 35 yrs ago, when I knew a lot less than I do now. I only have basic RCBS dies for my belted magnums, and my cases lasted well for the 4-5 times I reloaded them, with no separations, splits, or even enlarged primer pockets.