How much case stretch or shoulder movement is normal?

[Creedmore]

I have a .25-06 built on a Mauser 98.

Last year, while working up a new powder/load I had a case head separation. So this spring I'm going back to square one on my workup with all new brass. In the past, I had never measured the shoulder bump, just adjusted the full length die to kiss the shellholder, and move on.

Anyway, I had a gunsmith at the club check it out, and went to the range last weekend to burn some Remington factory ammo through it as a control test, and to get the scope zeroed. They were sticky on opening, which I though was odd.

Now the new workup. New WW brass, measured 1.925 on the bump gauge.

Loaded up for a ladder test: 110gr AccuBond, 49.1 gr H4831SC up to 51.0 gr in 0.3 increments, Federal Match primers.

Today: first two shots 49.1 and 49.4gr the bolt was sticky and hard to open, extractor marks on the case head. Signs of pressure on the minimum load.

Stopped shooting and went home. Been looking at the brass, and started measuring shoulders. Both the Remington factory ammo and my handloads measured 1.938" to the shoulder. Thats a stretch of 0.013! Was not expecting that. Also explains why my brass was overworked to the point I got the case head separation last year.

Now that I know the fired length, I can take more care, and set my full length die to only bump the shoulder .002" instead of sizing to die/shellholder contact. I may do this and shoot some minimum loads tomorrow.

My question -- is 0.013" a normal amount of movement? I'm concerned that my chamber is out of spec, maybe need to rebarrel or have the chamber recut.

Am I overthinking this? Why would I get a sticky bolt on factory or minimum loads?

 

[joelkdouglas]

Creedmore,

What are you measuring? To the datum line, i.e. for headspace, or to the shoulder?

If measuring to the shoulder, how are you taking that measurement?

1.938 inches is quite short of the headspace saami spec, but close to the 1.948 inches to the edge of the shoulder. However, I don't know of any tool that measures to the shoulder only.

Here's the saami drawing: http://www.saami.org/pubresources/cc_dr ... ington.pdf

It does sound like you have a problem somewhere, especially if factory ammo gives you a hard bolt lift. Those rounds are likely over 70,000 psi or thereabouts, for a pure guess.

I would likely take the rifle to a different smith, unless you trust the first one a good deal. Also, I would want him to look at the throat, as a short throat will also give the same indications.

v/r
Joel

 

[joelkdouglas]

Also, forgot to say welcome to the Nosler forum. A great group of guys here, and I'm sure someone will come along with some good info. I've never seen your problem myself.

 

[Creedmore]

Thanks, I've been lurking around here for quite a while. Finally got stumped enough to post. :wink:

The measurements I took were with a Sinclair bump gauge insert, so the measurement was to the edge of the shoulder, I believe.

I've had this rifle for 25+ years. Built by a friend-of-the-family gunsmith. Before the case head separation, bolt was smooth and never difficult to open unless you started to get close to pressure.

Now it appears to stick on everything. Is it possible the case head separation had some other affect on the bolt or chamber?

 

[SJB358]

Creedmore, I think you would be fine. It does sound like you have a tighter chamber width wise.. Not sure. It would be VERY easy to do a chamber cast though, just to get some specs. I think you should measure the internal capacity of the fired cases, against your new cases (same brand) to see what is going on there. You might have an overall tighter chamber that doesn't permit heavier loads. You are probably still getting the same speed, just using less powder. Always a good idea to just bump the shoulder .002" or so. Really lets that brass have a long life in my experience.

 

[300WSM]

welcome to the forum...


a few questions I would like to see you answer before you go any further..even in the thought process.

How many times fired was the case that got separated ???

Be honest here...how clean is the chamber? If you had a case split in the chamber well you are going to have a lot of brass debris still looming about. If you didn't get that all cleaned out then you need to do so and go shoot again. Extra debris in the chamber can make that tight.

Having that brass come apart in there is not going to now make the rifle have a hard bolt lift. It would be what is remaining after that that can make a normal feeling chamber as you said you had....to a tight one.

Look at the bolt face. Are you getting a lot of brass on the bolt face? Are you getting gouges out of cases where the bolt grabs them? If so then you have extractor problems and YES 100 percent that can make for a perception of a tight chamber/too much pressure loads.
People look past that extractor all the time and wind up selling a gun or never using it because they can't figure it out. Are the rounds ever hard to chamber before you shoot them. I mean a little tough to push in and close the bolt? If that is also an issue you have extractor problems.

Just a reminder that if you are trying to full length re-size...anything......just kissing the shell holder is not enough. You have to turn the die 1/4 turn after the kiss so it cams over.

 

[CatskillCrawler]

I have measured some of my rifle's brass growth after firing. I use factory ammo as my standard. Factory ammo all varies a little so I make all my growth measurements from the same lot so my baseline is controlled. I use the Hornady Headspace gauge kit which measures from the shoulders datum line.

270Win:
Federal 140gr Nosler AccuBond - .004" growth
Federal 130gr Fusion - .004"
Remington 150gr Core-Lokt - .005"

30-06 SPRGFLD
Remington 165gr PSP - .006"
Federal 150gr PowerShok - .006"
Hornady 165gr Interlock - .007"

22-250 Rem
Winchester 45 JHP - .012"
Remington 55gr PSP - .012"
Federal V-Shok 55gr SGK - .012"

358 WIN
Winchester 200gr SilverTip - .006"

25-06 Rem
Hornady 117gr SST - .005"
Federal V-Shok - 117gr SGK - .004"
Remington 120gr Core-Lokt - .005"

257 Roberts
Winchester 117gr PwrPnt - .005"
Hornady 117gr SST - .006"
Hornady 117gr Interlock - .006"

Not sure if it means much but the only rifle which I have measured that approaches your .013" growth is my Encore's 22-250Rem barrel. I would have your headspace measured. It can't hurt and it would eliminate that factor from your troubleshooting list.

I will say that I'm on the 8th reload on some of that 22-250 brass and haven't detected any issues to date and I shoot those with fairly stout loads.

 

[Creedmore]

Good questions!

How many times fired was the case that got separated ???
According to my log book, the separation was on the 4th loading.

Be honest here...how clean is the chamber? If you had a case split in the chamber well you are going to have a lot of brass debris still looming about.
I worried about that too at first. It's clean. I sent it to a gunsmith friend from the club and he didn't find anything leftover.

Look at the bolt face. Are you getting a lot of brass on the bolt face? Are you getting gouges out of cases where the bolt grabs them? If so then you have extractor problems and YES 100 percent that can make for a perception of a tight chamber/too much pressure loads.
I don't see any extra brass left on the bolt face or gouges in the case rims.

People look past that extractor all the time and wind up selling a gun or never using it because they can't figure it out. Are the rounds ever hard to chamber before you shoot them. I mean a little tough to push in and close the bolt? If that is also an issue you have extractor problems.
They do drag a little more than I remember before the separation. No force needed to close the bolt, just not as easy as it once was. On the minimum loads today, it was all I could do to get the bolt open. Thought I was going to need a rubber mallet.

Just a reminder that if you are trying to full length re-size...anything......just kissing the shell holder is not enough. You have to turn the die 1/4 turn after the kiss so it cams over.
That's one of the things that led to the overworked cases, I think. Before I had a bump gauge, I would adjust the resizer to kiss the shellholder + a little. Now that I can measure this, it is sized to 1.924" on the gauge. All of the fired cases measure 1.935 to 1.938. So the brass is getting pushed back quite a bit. Is the flaw in my thinking that I can adjust the FL die to only bump back to, say, 1.933?

Is it abnormal for the cases to stretch so much after firing? If the chamber was properly cut?

 

[Ridge_Runner]

here is what I would do
take a 25/06 case and run a .264 expander ball down in it, then screw your sizer up 3 or so turns, start resizing and trying it in the gun after each pass, if it won't go screw the die in a bit and repeat, do this till that case will chamber with just a bit of resistance, then screw the die in 1/16th turn and lock it down.
resize a case and load it with a mid level charge and fire, see if the stickiness goes away.
IMO, I think you are fireing a min. pressure load with slow burning powder in a case resized enough to leave you with excess headspace causing pressure spikes.
In a rem. 700 those rounds probably wouldn't even go off but the mauser CRF holds the case against the boltface to fire.
RR

 

[nvbroncrider]

To me it kinda sounds like a headspace/chamber issue. Got a .243 that had a chamber issue and required a hammer to get the bolt open from the factory using factory ammo. There was a small burr inside that caused the issue. So it does happen. But with what your saying it sounds like an oversized chamber to me.

 

[onesonek]

" But with what your saying it sounds like an oversized chamber to me."

Not overly familar with bolt guns, but that's sorta what I was thinkin.
What I would do,,,,,,, I take new brass and load one with a starting load, but only seat the bullet deap enough so that you have to cam it into the lands. Then with that fired case, set your FL to where you just barely bump the shoulder. Back the die off the shellholder at least a full 1/4 turn (might take a bit more), and start checking your sizing from there. Make a dummy round from that piece to set your die again, if you don't use the lock screw.
It certainly sounds like a you have some excessive headspace to me, and getting a fair amount of bolt thrust, even with factory loads. That makes for a bolt hard to lift. While not so excessive to fire, enough that your FL set to touch the S/H moving the should back a bit, and is allowing the brass to flow too much. That is what causes seperation. This could mean you will have to fireform each new piece.
But again, I'm a single shot guy, however bolt thrust and excessive headspace goes for either.

I could be wrong????

Did you have this built, or by it second hand?
Would you have a pic of the once fired factory stuff,,,unsized?

 

[300WSM]

You don't go from having a perfectly fine chamber to non in a matter of one shot...case head separation or not.

Chambers are not like that. They are not a wear item like a barrel.

If your chamber was fine before the shot...its still fine but either distorted with debris or you have an extractor issue. People dismiss the extractor all the time because it just doesn't make sense to them.

make sure you have it super cleaner with some compressed air (yes the air tank in the garage works great) and make sure it isn't now too sharp and or grabbing too much of the case.

 

[onesonek]

All good points.
Somehow I missed RR's post,,,,necking up and down, is good way to fire form also. And in many ways the easiest, if you have the expander button on hand. But llike others noted, if the chamber is clean.
Another ?,,,, when you had seperation, what was used to get the stuck brass out?

 

[Ridge_Runner]

This is my guess to what is going on
slightly oversized chamber causes a min. load to be underpressure causing pressure spikes. and I assume the problems started when H4831 shortcut was used for the first time, why else would he be shooting a minimum load? my post above will fix this.
RR

 

[300WSM]

This is my guess to what is going on
slightly oversized chamber causes a min. load to be underpressure causing pressure spikes. and I assume the problems started when H4831 shortcut was used for the first time, why else would he be shooting a minimum load? my post above will fix this.
RR

RR,
I would say that could be a possible but...

"I've had this rifle for 25+ years. Built by a friend-of-the-family gunsmith. Before the case head separation, bolt was smooth and never difficult to open unless you started to get close to pressure.

Now it appears to stick on everything."

So if he is using factory ammo..and getting this ..now what? A lot of factory ammo is not shy about velocity/pressure.

Moreover how does his chamber on one shot go from being a smooth sailing chamber to suddenly now everything sticks.


Back to the original poster.....

What happens when you chamber a round....and then unload the same round WITHOUT shooting?? Also, as I asked before if you can remember what it felt like to chamber a round before all this...and how does it feel now when just chamber it. Is it harder in any way to chamber a round...factory round..than it was before?

 

[CatskillCrawler]

Any way you look at it, a growth of .013" is excessive and I doubt will pass a headspace test.

Being that it is a converted mil rifle, you have no idea how many rounds have been through this rifle. It is possible for your bolt lugs or recesses to be worn or setback. I believe you would see the wear on the bolt lug bearing surface. Excessive headspace will exaggerate the forces placed on your bolt lugs. If the wear is in the lug recess areas, you can eventually wear thru the hardened metal of the receiver. I doubt this would happen without seeing issues on your bolt's lugs though.

When you cleaned out your chamber after the case failure, did you leave any oils or lube in the chamber area?

 

[Creedmore]

Did you have this built, or by it second hand?
Would you have a pic of the once fired factory stuff,,,unsized?

This was built for me when I was 16, back in 1987. It has taken many TX whitetails, shooting 100gr Sierra Gamekings, including my son's first two deer. (This is his gun now). But it's never really been a consistent tack-driver.

Hunting more open spaces now, going to heavier bullet, longer range ability. Trying to squeeze all the accuracy and ballistics I can get out of it. Thus, trying Accubonds and want to try Berger HVLDs if I can get out of this rut I'm in. It has a 1:10 twist, 22" barrel.

Here are 3 pictures I just snapped of one of the 100gr Remington factory rounds I fired last week. You can clearly see the stretch mark in front of the web.

 

[Creedmore]

What happens when you chamber a round....and then unload the same round WITHOUT shooting?? Also, as I asked before if you can remember what it felt like to chamber a round before all this...and how does it feel now when just chamber it. Is it harder in any way to chamber a round...factory round..than it was before?

I feel no difference closing/closing the bolt on an empty chamber, or opening/closing the bolt with a live round. Opening the bolt has always required a little bit of effort -- trying to put this into words -- this rifle has never been so smooth that you can fire a round and cycle the bolt while staying on target, in the scope.

Opening the bolt on the fired factory remingtons required me to rest my right thumb on top of the scope to get leverage on the bolt handle as I pulled up.

Any way you look at it, a growth of .013" is excessive and I doubt will pass a headspace test.

That's what is making me scratch my head. Maybe its just a sloppy mil-surplus action?

I'm going to clean the lugs/chamber once again for good measure. Maybe there is still debris in there, but I can't see any. May go to the range tomorrow with a different box of factory ammo. I'll pull some bullets and measure the shoulder, seating depth before firing.

Thanks for the replies, everyone.

 

[PJGunner]

Any way you look at it, a growth of .013" is excessive and I doubt pass a headspacewill test.

That's what is making me scratch my head. Maybe its just a sloppy mil-surplus action?

I'm going to clean the lugs/chamber once again for good measure. Maybe there is still debris in there, but I can't see any. May go to the range tomorrow with a different box of factory ammo. I'll pull some bullets and measure the shoulder, seating depth before firing.

Thanks for the replies, everyone.[/quote]

I'd take a close look at cleaning out the lug slots that the bolt lugs slide into. I have a very tight chambered FN mauser custom 30-06 built by the late Cal Albrite, an amature gunsmith that had a reputaion of being a fantastic metal man back in the 1970s in the Northern Nevada area.
If any dirt or debris gets into that lug slot, bolt lift gets to be very stiff exactly like you're describing.

"Just a reminder that if you are trying to full length re-size...anything......just kissing the shell holder is not enough. You have to turn the die 1/4 turn after the kiss so it cams over."

I'm sorry but I have to disagree with that. If I set up my dies in that manner, I'd be creating headspace problems in most of the rifles I own that that includes those with match grade chambers. I changed my methodof full length sizing when I learned that the belt on magnum brass wasn't worth a damn for headspacing and set up my dies to headspace on the shoulder. Now I set up all my dies to do this for bottleneck cartridges.

This is how I set up my sizing die for bottleneck cartridges.

1. Take a once fired factory round and blacken the neck and shoulders with a Magic Marker or Sharpee pen. Some people like to smoke the neck and shoulder, but I find the Magic Marker/Sharpee pen a bit better.

2. Carefully lubricate the case.

3. Loosen the lock ring on the sizing die and back off about two turns from when the die is set to touch the shell holder.

4. Size the case. Note where the marks are on the case and turn the die down about a half a turn and size again. Turn down some more, and resize again. What you are looking for is the marks on the blackening just touching the shoulder.

5. Clean the lube from the case and try it in the rifle. It may chamber just a bit on the snug side. If so, turn the die down ever so slightly, lube and size again. Wipe off the lube and try in the rifle. If it slides in as easily as a factory round, you should be good to go. If not, usually one more very slight adjustment should fix the problem.

6. Tighten the locking ring for the die and you're done. You have just set your sizing die up for a custom fit to your specific rifle, rather than a generic one size fits all guns.

Paul B.

 

[rick smith]

PJHunter has given you the correct method to set your FL dies commonly called Partial FL sizing. Gave up the normal instructions for cam over years ago when I seperated cases in two different rifles one a 300Win Mag and one a 308Win. It may be necessary in some cases but in none of the rifles I own or load for.Rick.