How much case stretch or shoulder movement is normal?

[Con]

Creedmore,
There's one more situation that can cause head separations and appear as a headspace issue when it's not. If your chambers base is wider than the brass being used, the brass will expand and stretch to fit the chamber, resizing it then brings it back, firing makes it stretch again and the brass usually lets go somewhere between shots 2 and 5 depending on how hot your loads are.

This issue is most prevalent in European chamberings like say the 6.5x55 primarily because US manufacturers insisted on making brass with a solid head size of 0.471" (and dies that match) when the true European specs are 0.480". Firing US brass in a Euro spec'd chamber and reloading it using dies made to US specs caused all sorts of trouble. Not sure if that's still the case though.

It's not relevant to your issue though as you've measured the brass as having grown in length rather than circumference, but its worth keeping in mind.
Cheers...
Con

 

[Creedmore]

Does that make it a bit clearer?
Cheers...
Con

Excellent explanation. Thank you, makes perfect sense. Nice little trick.

 

[Oldtrader3]

I still do not have any idea what you know about your chamber dimensions, your FL sizer die dimensions, shell holder stack dimension to the shoulder datum, or what the headspace dimension of the case is, measured at the datum on the shoulder from base of the rim. In other words, I can not get to where you are from where you have described to your problem per normal measured values.

You are using a tool that references a dimension which may or may not have anything to do with headspace, depending on who made this fixture and what it is measuring which obviously is not headspace. The important fact is that you do not know what your headspace is for this rifle and until you have that measurement, or have gauged it with a go/no go set and a field gauge, you do not know if you have a safe situation with regards to headspace or not?

Having excessive pressure signs on light load with a 110 grain, .257 bullet using 49.0 grains of H 4831 SSC should not be a pressure issue and is indicative of a deeper issue here which has not been discovered and described as yet.

I would not shoot any more cartridges in this rifle until a competent gunsmith has measured headspace in your rifle's chamber and measured your handloads for length and other pertinent dimensions in a gauge block so that you know where you are dimensionally from the chamber dimensions to the cartridge dimensions. Something is not right and I surely can not tell from this information given what the problem is?

Sorry, but I can not discern where you are dimensionally or even what your issues are without a set of tooling and micrometer measured dimensions from a properly made chamber casting or dial indicator fixture measurements of your chamber and fireformed cases. So far, you have just confounded me with information which has no relevance to the suspected issue at hand.

 

[Guest]

I think Charlie is on to something here. You're not measuring the headspace with that gauge you have. What you're measuring is the distance to the shoulder junction, which is not the headspace dimension. What you need to measure the headspace dimension on a fired case is the Hornady LNL headspace bushings:

http://www.hornady.com/store/Headspace-Gauge-Bushings

and even that is not an exact measurement. It will get you close enough to avoid blowing yourself up, but I tend to think you might have a setback issue with the bolt and lugs that is causing you headspace problems. I'm not sure if that's fixable (a metallurgist or competent gunsmith can tell you) but it might be. Perhaps having the lugs lapped and then re-heat-treating the action would do it? But then you have the issue of warpage to contend with, so I'm not sure. Anyway, what I'd do is spring for the proper headspace gauge from Hornady (for the 25-06 it would be the "C" bushing (.375"). Then if the measurement you get is well outside the 2.0456-2.0526" range for SAAMI spec for 25-06 brass, you should have the rifle checked for headspace by a competent gunsmith with the proper headspace gauges.

Once you establish the rifle is safe in terms of headspace and the bolt has not set back into the lugs (it is, after all, a mil-surp mauser, and might have age-related issues) you can move to getting it set up properly to shoot. Otherwise, you're going to stretch the living crap out of your brass upon first firing, and run the risk of another casehead separation and potentially physical damage to your rifle and/or your son's fingers, eyes, face, or worse.

Safety first! Always.

 

[elkeater2]

I read the whole thread and read it again. I'm glad that apparently you have formed and sized brass that fits. What still concerns me is the brass was formed from brass that was maybe initially undersize for the chamber and got stretched too much on the first firing. I looked at the pictures of the Remington 100 gr. fired case with the caliper, and the one that separated. That sure looks like a stretch mark to me. I use a Dremel with a reinforced cutting wheel to section cases and that's what I'd do to that one. Did you fire any more factory rounds after the total cleanup? Still stretch marks? Hard bolt opening after firing them could have been due to leftover carbon, powder residue, etc. along with brass particles.
IF that factory case was overstretched on first firing then:
The factory rounds are undersized
or the chamber is oversized
or both
or the lugs have set back, or the mating area in the receiver is worn.
All the advice about setting dies, using larger expanders, etc. is valid, but the fact remains that if a set of factory manufactured ammo stretched that needs to be addressed. For now, you are loading for a 25-06 wildcat, needing specially prepared brass only fire-formed in the chamber from cases that were initially set up tight through use of expanders or .270 or 30-06 cases.
Nearly any gunsmith out there has actual go, no-go headspace gauges, and you can even rent them cheap. Seems like a good place to start.
If you don't want to change the rifle, I'd suggest trashing all the brass and picking up on the Shooter's Pro Shop .270 Win. blems for $34.45 for 50 count. That's a good deal. That way you could really start from fresh, using the same technique on all of them. My best .25-06 cases have been W-W formed from .270 Win. which I settled on for my Encore.
Elkeater2

 

[Creedmore]

Go & No-Go gauges will be here in a couple of days, along with the Hornady headspace insert.

I'd rather be safe than sorry. I'll pick up another box of Remingtons, pull a couple of bullets and measure everything so there is a before/after set of measurements.

To be continued . . . . :wink:

 

[SJB358]

I will add this, and I am only saying it cause I had it happen to me with the SAME exact factory ammo. I had a BRAND new Remington M700 25-06 CDL. I had a devil of a time making it shoot till I did a bunch of work to it. I bought one box of the 100 grain Core Lokts and 4 out of a box of 20 would not even chamber and fire they were that much oversized.

I agree, the rifle should be checked, but then again, the factory ammo should be checked as well. I am not a Remington fan for ammo or rifles due to all of the struggles I had with this rifle. I check everything now. I think a simple chamber cast would tell you alot and not be expensive. It is something you can buy from Brownells and do yourself and it is reusable if needed.

Good luck with the rifle. Not much that can't be fixed if a good smith puts his mind to it.

 

[woods]

Just to throw some things out there for consideration

A case does not fully expand on the first firing. A typical sequence of events can be illustrated by measurements taken on my 30-06 with a Hornady insert

New case - 2.040"
Once fired - 2.0485" - neck sized
Twice fired - 2.050" - neck sized
3 times fired - 2.051" - slight crush fit - neck sized
4 times fired - 2.0515" - crush fit - push shoulder back .001" for very slight shoulder contact in chamber

Next, the measurement with the Hornady or similar insert should fall close to the datum line

unlike a pic I saw earlier in the thread

The go-no-go-field type of headspace gauges will only tell you if your chamber is within spec or not. The Hornady insert and similar gauges along with the RCBS precision mic and the Wilson will give you actual measurements to show the relationship of your cases and chamber.

Seating into the lands will not prevent the case from moving forward in the chamber to take up all available headspace. The firing pin is one force that will push it forward but by far the primer exploding in the primer pocket is a much greater force and will move the case forward and even set the shoulder back a couple of thousandths

http://www.btgresearch.org/High-speed%2 ... 0waves.pdf
http://www.lasc.us/Brennan_6-7_Headspace.htm

I've produced similar results with setting the shoulder back a couple of thousandths when firing a live primer only in a case but no movement from firing pin strike on inert primer


Last normal head clearance for an unbelted case is considered to be between .002" and .008", which is the measurement between the case shoulder and chamber shoulder with the case head against the bolt face. But it can be over that and not be a problem. The 30-06 with the measurements above had .0115" but it still shoot lights out

 

[Oldtrader3]

Good luck with that .25-06, it sounds as though you are on the right track to getting it taken care of. I hope that it is nothing that can not be easily fixed and get you back shooting it again.

 

[Creedmore]

Well, my Forster go & no-go gauges arrived today.

The no-go chambers just as smooth as buttermilk . . . .

I thought for sure this was a waste of time, but alas - it looks like I'll be having the barrel pulled to recut the chamber or rebarrel as something else.

Thanks for all the discussion. I learned alot on this one, didn't think there was any chance it would end up like this.

 

[Oldtrader3]

I am just happy that you are healthy, safe and did the right thing. I was very worried that that chamber was enough out of spec enough to be a problem when you got high pressure signs from that 49 grain starting load which you listed. You did what you needed to and got the tooling that you needed to find out where your chamber dimensions actually were.

Good luck with having the rifle rebarreled or just rechambered, whatever you decide. The .25-06 is a fine cartridge. I owned one myself for quite a few years and killed many prairie dogs and deer with it. Let us know when you decide what to do and get the work done, how that rifle shoots then! Good luck with that.
Charlie

 

[Guest]

Well, for whatever it's worth, you're doing the right thing. While your gunsmith has the rifle, have him check the lugs on the bolt and in the receiver to be sure you don't have some setback. This being an old mauser action, there is the possibility that you've gotten into the lugs a bit over the years and perhaps past the heat treat into the soft portions. With any luck you have a barrel that wasn't set up properly in the first place, and perhaps the smith can just check everything, set the barrel back a few threads, and re-ream your chamber. That would be the most cost effective option, I suspect, plus it would save you the hassle and cost of refinishing everything, recutting the barrel channel in the stock, and so forth.

I'm with Charlie - the best part is, neither you nor your son lost a finger or an eye, or worse, and you now have a great appreciation for how firearms work and how to diagnose a bit in the future if you run into sizing problems or a loose chamber on a rifle you pick up somewhere along the way.

Keep us posted on the progress and outcome. And post some pics when you're done. We all love rifle porn!

 

[HTDUCK]

Gene
Time for that 280AI buddy...........

And you need to post up a pic of the rifle anyway.A before and after kinda thing..... :mrgreen:

 

[Creedmore]

Gene
Time for that 280AI buddy...........

And you need to post up a pic of the rifle anyway.A before and after kinda thing..... :mrgreen:

Howard, I wondered how long before you chimed in. 280AI . . . quit trying to corrupt me.


My son is wrong-handed, so I inletted and finished-out a gray laminate LH thumbhole stock from Richards Micro-Fit a couple years ago. Here she is as .25-06 :

 

[Guest]

Man, Creedmore, that is a sharp rig! I would have the existing barrel set back a few threads and the chamber re-cut in 25-06, and go from there. There's nothing wrong with that setup at all except the headspace issue. (That is all providing there is no need to deal with lug setback in the bolt/receiver, of course.)

 

[SJB358]

That is a very nice rig! I agree with Dub, get it tuned up and hunt it. That rifle is a looker. You did well with it. Love that stock.

 

[DrMike]

Creedmoor,

Good looking rig. Should be an easy fix for you.

 

[IdahoCTD]

The headspace isn't really a issue as long as you know about it and don't use factory loads. By necking up to .264 and then back down you create a false shoulder to keep the brass tight in the chamber (if you don't you get case head separation like you experienced). When I do it I make sure there is resistance when closing the bolt. You can use your neck sizing die for this operation and your FL die to size it after fireforming. The same thing has to be done for Gibbs wildcats or any others that move the shoulder forward. If it shoots .5" keep shooting it. Now you know not to set the shoulder back too far with your dies. Worry about a new barrel when that one wears out. It wouldn't be a bad idea to have a smith check the condition of the action but I'd keep shooting the barrel if the action is good.

Brass loses it elasticity after every firing and that is why it wears out. That is also why it stays larger after each firing and why case necks have to be annealed.

You cleaned the action out well but did you lube the back of the bolt lugs? It's a good idea to prevent galling and it makes opening the bolt a bit easier.

 

[HTDUCK]

Man, Creedmore, that is a sharp rig! I would have the existing barrel set back a few threads and the chamber re-cut in 25-06, and go from there. There's nothing wrong with that setup at all except the headspace issue. (That is all providing there is no need to deal with lug setback in the bolt/receiver, of course.)

Naw, he needs to rebarrel it and sell me the take off barrel.
I got a 250 Savage itch needs to be scratched. :shock:

Howard

 

[woods]

The headspace isn't really a issue as long as you know about it and don't use factory loads. By necking up to .264 and then back down you create a false shoulder to keep the brass tight in the chamber (if you don't you get case head separation like you experienced). When I do it I make sure there is resistance when closing the bolt. You can use your neck sizing die for this operation and your FL die to size it after fireforming. The same thing has to be done for Gibbs wildcats or any others that move the shoulder forward. If it shoots .5" keep shooting it. Now you know not to set the shoulder back too far with your dies. Worry about a new barrel when that one wears out. It wouldn't be a bad idea to have a smith check the condition of the action but I'd keep shooting the barrel if the action is good.

x2

Forming a false shoulder

Is not that hard. I have done it for a 30 Gibbs and a few other calibers and it will keep the case from moving forward in the chamber during firing and make headspace a moot point