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Discussion Starter #1 (Edited)
I had a couple of 6.5 x 55 case head partial separations with new Lapua brass and moderate handloads shot in a VZ24 with a new Brownells barrel. The rest of the cases show slight radial stretching/ring at the end of the web. Bent wire interior scratch tests are ambiguous...it catches on some cases but not others.

I pulled the headspaced barrel to drill and tap the front ring for scope base. It was not super tight and I retorqued it firmly. The bolt closes with barely noticeable resistance on the GO gauge. The Clymer GO gauge does not exceed the long dimension in my Lyman case length gauge.

Once fired Lapua brass exceeds the long dimension of the Lyman case length gauge regardless of the load. New Lapua brass, same batch, does not exceed the long dimension. I checked the brass from the starting load for a ladder load series and that case had stretched beyond the long dimension of the case length gauge.

I cannot find the test cases provided by the 'smith who set the headspace on the barrel but do not recall there being any indications of case stretching.

At first I thought the rear chamber diameter might be a bit too large, but would that account for the obvious case length increase? Bolt lugs don't show setback and I did not shoot hot loads. Did I get some debris between the end of the barrel shank and the receiver shoulders? The barrel shoulder appears to be seated on the end of the receiver.

I would appreciate any thoughts on case stretching problem before I ruin any more brass and ask the gunsmith to set the barrel back a bit.
 

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Probably a headspace issue causing case to stretch. All chambers are not bored the same in that chambering, so I have recently read somewhere.
 

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It pretty much sounds like it has to be one of two problems. Either the chamber is over spec. for headspace or your bolt is setting back from the breech thrust when fired.
On a bolt action you should be able to take a fired case and put it back in the gun and close the bolt without a lot of effort.
I would bet you can't do that with your rifle.

jedman
 

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Discussion Starter #4
Yes, there is a lot of variability in Swede chamber dimensions, but I'm using new brass which has not been shot in another rifle and which has not been full length resized.

I'll see if a fired case rechambers.
 

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Now I would see if those same fired cases fit the cartridge gauge.
The only way I can see a case head separation happen is to have severe headspace ?

You could try priming a new or resized case and firing it and see if the primer is protruding out past flush with the end of the case.

I have had brand new Norma brand brass that would not chamber without being resized. So all new brass isn't always correctly sized either.

jedman
 

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Discussion Starter #7
Lapua cases fired in the Brownells barrel drop all the way into the case length gauge. Identical load fired in a M70 6.5 x 55 did not show web expansion ring. Identical load fired in another VZ 24 with unknown 6.5 x 55 takeoff barrel (mounted by the same shop which did the Brownells barrel but maybe 30 years ago) had some web expansion but would not drop all the way into the case length gauge.

I'll try some primer only shots as Jedman suggests. This might shine light on the oversized chamber theory.

Case length gauge fit suggests the Lapua brass is correctly sized. Will also smoke/mark shoulder of new brass to assure it is seating on the should of the length gauge. I recall having some domestic 6.5 x 55 brass which had undersized .473 case head size and which showed web expansion...but understandable given the head and base dimension.
 

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The first thing I would do, and I've done it before, is seat a bullet at the lands and the case base on the bolt breach, and fire it using a mid size load. If that case then chambers in the rifle, neck size it, reload it with its normal charge & jump, and fire it again. For all practical purposes You now have a chamber cast of Your rifle. Don't worry about spring back, this is close enough for what You want to know. The only gauge I care about is the chamber of the rifle. This spent case can now be measured in all its dimensions for die settings, etc. In Your case, Im willing to bet this spent case will not fit in Your gauge. Case base separation almost always means excessive head space. A rifle chamber, reloading dies, and case gauges, separately manufactured, have too much potential for tolerance stacking to have any value for Me. This spent case is what I go by.

Serious target shooters start with a chamber reamer, fire cases in the finished rifle, send them off to have custom dies made, and custom chamber gauge if desired. Now You have something. Not a collection of so called SAMMI components with their range of tolerances that could easily be incompatible.

The method I suggested can get You where You need to be...Good Luck 🙂
 

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Discussion Starter #9
Now I would see if those same fired cases fit the cartridge gauge.
The only way I can see a case head separation happen is to have severe headspace ?

You could try priming a new or resized case and firing it and see if the primer is protruding out past flush with the end of the case.

I have had brand new Norma brand brass that would not chamber without being resized. So all new brass isn't always correctly sized either.

jedman
Primed a couple of new Lapua cases and fired them. Detectable primer protrusion resulted. Clymer No Go gauge is on the way from Brownells.
 

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Discussion Starter #10
All the Lapua cases, even the ones with head separation, fired in the Brownells barrel will slip all the way into the case length gauge whether they are neck sized or not.

Lapua cases fired in a M 70 push feed also fit in the case length gauge but ones fired in an older barrel of unknown origin on another VZ24 will not due to radial case expansion in the rear quarter of the case.
 

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Discussion Starter #11 (Edited)
I almost purchased yet another VZ24 action at the Mason Gun Show today but declined when I looked at the bolt lug recesses from the front of the action. One seating face did not have a wear mark indicating full contact by the bolt lug. The other seating face was well worn and I could feel a definite bump when I dragged a pen tip from the worn area to the adjacent non contact surface. Could not tell if this was just high use wear or setback from high pressure load/normal load through very rough (as described by vendor) barrel.

Just too much difference between the two lug seat faces. Someone else bought it....hope they don't have problems with it.

I'm going to check the Brownells 6.5 x 55 barrel chamber with a No Go gauge, but am anticipating pulling the barrel to check bolt lug recess seats and to see if any debris from scope base drilling and tapping was caught between the barrel end/shoulder and the receiver.
 

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Discussion Starter #12
No go gauge arrived from Brownells. It is a Clymer, same as my Go gauge. The bolt won't close on the no go. Hmmm.

I think the next step will be to try some different brass. I have new Norma 6.5 x 55 brass and might be able to scrounge some new Winchester brass. Also might try some once/twice fired domestic cases.

Considering a chamber cast but uncertain what that will show that the gauges don't. Maybe chamber diameter, but if that were out of whack the cases wouldn't fit in the case length gauge.
 

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I have an old M96 Swedish Mauser that I've shot a fair number of factory loads thru. Some Norma, Winchester, and even Herter's brands. Never a problem whatsoever. A while back I bought a box of Prvi Partisan and bolt lift after firing was very hard compared to normal. Only fired 3 rounds, as obviously something wasn't normal. Fired a few rounds of Winchester I had on hand and everything was normal again.

No idea why the Prvi's caused a problem and didn't try to figure it out, I just quit using them.

I know this doesn't help your problem, but just saying sometimes weird things happen. My problem was easily solved by avoiding the one brand of ammo - your problem, unfortunately, is more complicated! Hope you get it figured out.
 

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The first thing I would do, and I've done it before, is seat a bullet at the lands and the case base on the bolt breach, and fire it using a mid size load. If that case then chambers in the rifle, neck size it, reload it with its normal charge & jump, and fire it again. For all practical purposes You now have a chamber cast of Your rifle. Don't worry about spring back, this is close enough for what You want to know. The only gauge I care about is the chamber of the rifle. This spent case can now be measured in all its dimensions for die settings, etc. In Your case, Im willing to bet this spent case will not fit in Your gauge. Case base separation almost always means excessive head space. A rifle chamber, reloading dies, and case gauges, separately manufactured, have too much potential for tolerance stacking to have any value for Me. This spent case is what I go by.

Serious target shooters start with a chamber reamer, fire cases in the finished rifle, send them off to have custom dies made, and custom chamber gauge if desired. Now You have something. Not a collection of so called SAMMI components with their range of tolerances that could easily be incompatible.

The method I suggested can get You where You need to be...Good Luck 🙂
Yes sir I believe you got it! Just mark all of the brass that is fire formed to the oversized chamber so have it designated to that rifle only and call it good.

Back in my coyote hunting hay day I shot out the barrel on my tang safety Ruger 77 243 twice. The second time it came back from Ruger with a sloppy chamber. I did exactly as Conch just suggested and neck sized only. That rifle still rides around in my truck on cold winter mornings. The coyotes can't tell the difference.
 

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Discussion Starter #15 (Edited)
I sure appreciate everyone's input. Tricky rifles that show promise have to be regarded as a challenging learning experience even if at times one is not sure what one is learning! Or what one has forgotten from long ago lessons. I embarrassed myself terribly removing the VZ 24 bolt guts so the headspace gauge could be used. While removing the bolt sleeve, cocking piece and firing pin I managed to slip with the main spring partially compressed and the cocking piece sear caught the tip of my index finger....blunt surfaces can cut!!! This bolt has a Buehler safety installed and disassembly is not as easy as with the military safety....I remembered to insert a penny between the cocking piece and the bolt sleeve to unscrew the firing mechanism only after the fact.

The Lapua brass I've been working with is either new or once fired and neck sized only.

Tonight I found a few rounds loaded for another rifle with new Winchester brass and a box of new Nosler brass. Also some Norma ?once fired brass. Later in the week I'll have a chance to shoot some of them in the Brownells barrel.
 

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Discussion Starter #16
I have an old M96 Swedish Mauser that I've shot a fair number of factory loads thru. Some Norma, Winchester, and even Herter's brands. Never a problem whatsoever. A while back I bought a box of Prvi Partisan and bolt lift after firing was very hard compared to normal. Only fired 3 rounds, as obviously something wasn't normal. Fired a few rounds of Winchester I had on hand and everything was normal again.

No idea why the Prvi's caused a problem and didn't try to figure it out, I just quit using them.

I know this doesn't help your problem, but just saying sometimes weird things happen. My problem was easily solved by avoiding the one brand of ammo - your problem, unfortunately, is more complicated! Hope you get it figured out.
Thanks Spruce. I recall reading somewhere that the Prvi Partisan loads were a bit hotter than US domestic loads. Herters imported some of their merchandise from Europe but I don't know about their ammo offerings.
 

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Pondering.... a rough chamber can hold onto the brass not letting it slide back to the breech face when fired. If the neck end of the brass is grabbing the chamber and the web end is slipping, that could cause head separation since only 1 end of the brass is able to stretch/expand. The only other idea is what others have already said, maybe your chamber is oversized. Maybe the gunsmith let his finish reamer wobble when finish chambering the barrel??


Rosewood
 

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One problem with living with an oversized chamber is if you ever sell the gun or give to your children, if they use factory ammo, they may have the same problem.


I bought a .260 rem barrel for my Encore. Stupid thing was separating case heads. After some measuring, I figured out the chamber was too deep with too much headspace. Sent to TC/S&W and they said it was within spec. So I ordered a no-go gauge and did some more testing. Sent it to them again explaining all of my measuring, they then decided it had too much headspace. It seems like the no-go gauge was like 0.015" below the breech face in the barrel. Guess the first gunsmith had too much headspace.....


I could have just fireformed my brass and lived with it, but then using factory ammo becomes an issue. Since they no longer made the .260 barrel, I asked for a 7-30 waters contender barrel which was on my wish list anyway. Happy camper now.


Rosewood
 

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Discussion Starter #19
Finish reamer not to spec or wobbling had crossed my mind. If I'm using my Clymer go and no go gauges correctly then headspace is OK. I'll break out a magnifier and look at the case necks, there doesn't seem to be a problem there to the naked eye.

Shot Nosler and Winchester new brass today and there did not seem to be excessive radial web expansion, but I'll measure them to confirm that observation.

Things seem to be pointing to soft Lapua brass or chamber diameter out of spec.
 

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M 134, You have a strange problem for sure. One last thing I thought of is the diameter at the head of the brand of brass that has sepparated the correct size for the 6.5 X 55 ? I heard somewhere that some were made with the same diameter head such as 308 Win. size and that would be 7 to 8 thousands undersized.

jedman
 
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