Head Separation on straightwalled cases

[Ironduke]

This is the closest forum group I could find, and I figure someone here will know the answer. It's not a case forming question per se, but it has to do with case sizing.

My 458 Lott brass only lasts 2-3 firings before the brass has a stretch ring inside. Rifle is a CZ 550 and is factory all the way. Since the Lott only head spaces on the belt, I can't really figure out how the cases are stretching above the web. I guess it is possible the chamber is too deep at the belt allowing the case to be pushed forward by the firing pin. This would allow the case to seal the chamber, and stretch back to the bolt face.

I may have answered my own question. I guess I need a set of go/no-go gauges. Then maybe I can find brass with more generous belts? Or have the barrel set back a turn and rechambered to minimum spec.

Any other thoughts?

Paul

[country gent]

Yes have the headspaced checked, and adjusted as needed. Another cause of head seperations is the pressure your loading to, lighter loads last longer than full power loads. Another is the brass itself some are softer than others in the head area. Alot load the belted mags to headspace on the shoulder instead of the belt to extend case life. On the Lott I dont think there is enough shoulder there. Possibly load out to the bullet touching the rifling to hold cases snug against the bolt face would help.

[243winxb]

Interesting. What happens if you dont run the case all the way into the Full length die? But just enough so you feel the expander open the case mouth?? This would give enough neck tension to hold the bullets, maybe? And not over work the brass?? http://www.saami.org/PubResources/CC_Drawings/Rifle/458%20Lott.pdf Just thinking out loud.

[243winxb]

http://www.accuratereloading.com/ Check the forums at link. "Big Bores"

[runfiverun]

the Lott is a tapered case.
I'd look at how much I'm sizing down the case. [fired versus sized]
and how short it is to the chambers mouth.
to reach the end of the chamber the case has to grow about .02 to get there from trim length.

I'd try not re-sizing the full length [neck sizing] and see if those cases last longer.
imo this is like the 303 brit. where full sizing is just too much stress on the case.

[Artful]

On 2-3 reloadings getting case head separation - I'd also say head space issue.
You could see if you can find an O-ring to put in front of the belt like we do for 303 fire forming to see if it makes a difference.

[Frank46]

Never fooled with belted cases but sound as though the recess cut for the belt might have been cut to deep. This would allow the case to extend further into the chamber and upon firing the back end of the case expands till it contacts the bolt face. Don't know if this makes sense but there it is. Frank

[runfiverun]

it makes sense in a way.
the cases are for sure stretching and flowing somewhere.

[Dan Cash]

Check your headspace first. Then, try some different brass. I don't own any belted calibers but have reloaded .300 H&H and 7mm Rem for friends and have noticed difference in the belt width/location on different lots of brass. With the bottle necked cases, I set them to headspace on the shoulder. I suppose that one could headspace the Lott on the case mouth like .45 ACP or .300 Blackout.

[rbuck351]

Yeah, it's gotta be head space. Try putting some paper shims between the bolt face and the case and see how much head space there is. It's not 100% accurate but will give you a fair idea of what you have. A resized empty case should work fine.

[GONRA]

GONRA read decades ago the "belted cases" hava reputation for short case life before head separations. There's one hellave "stress concentration" at the belt/case body junction....

Pretty sure "belted cases" started out with British Holland & Holland huntin' calibers,
in the mercuric primer era, so no reloads.
(Mercury embrittles cartridge case brass.
Brits stuck with corrosive, mercuric primers for a looong time.
Wealthy hunters were NOT reloaders so didn't care...)

Lateron, U.S.&A. Reloaders did care.

(All you historical experts out there can check this for accuracy....)

[Artful]

Yeah, it's gotta be head space. Try putting some paper shims between the bolt face and the case and see how much head space there is. It's not 100% accurate but will give you a fair idea of what you have. A resized empty case should work fine.

Don't forget to remove your extractor if your going to do this and different paper comes in different thicknesses

http://www.casepaper.com/resources/charts/paper-thickness-caliper/

http://hypertextbook.com/facts/2001/JuliaSherlis.shtml

[tygar]

Get the "Innovative Technologies" (I think thats the name) belt sizer die. I use it on all my belted mags & don't think I've had hardly anymore separations. Hot loads shorten case life so this really works well, I usually start with hot & work up. You must use a superior lube like Imperial to size. Check all the other stuff above, but I have a bunch of straight cases, 450, 458, 458 Lott, 450 Watts & I find they don't separate anywhere near as much as 375 H&H & 300 Win or Wby, so some other factor may also be involved. But I will guarantee the belt sizer is needed. The shorter belted's also seem to have less head separation.

[Lead pot]

I went through this last year with a new batch of brass.
What I found was thin case walls and the bases where undersized for the .45-2.6 cases. The base diameter was .496" and most .45 chambers run from .500 + a little. My chamber at the base is .500"
Some of my brass pulled apart about 1/2 way on the case and the brass was .004" thick at the point of failure and the case mouths where .010"
You might say I had moisture in the chamber or case lube I did not wipe off, but this is not the case. I do not size my brass after the first firing. and I do not have a head space issue.
I cut a couple cases and send photo's to the manufacture that made the brass and told then I would send the cases for them to check out what is going on but no response back from them.
Head space could be the problem but that is not always the case. Short cases for the chamber and a tight crimp on the bullet will also pull the case as well as a case to long will pull the brass when it gets past the 45 degree chamber end and this also crimps a bullet tight enough that it will stretch and at times separate a case.
Base diameter to small for the chamber base will expand the case base and it will form a ring that gets sized back down it one full length sizes the case and in a few shots fired that portion of the case will get thin and crack.
The sure way to find out what is going on is split a case and take some close measurements.

http://i704.photobucket.com/albums/ww43/Kurtalt/th_IMG_2339_zpsylmw7wen.jpg (http://s704.photobucket.com/user/Kurtalt/media/IMG_2339_zpsylmw7wen.jpg.html)

http://i704.photobucket.com/albums/ww43/Kurtalt/th_IMG_2411_zpsu9eib1nn.jpg (http://s704.photobucket.com/user/Kurtalt/media/IMG_2411_zpsu9eib1nn.jpg.html)

[EDG]

I have been shooting 45-70s since 1972. My cases fail due to body splits from excessive sizing.
I have never had a separation with close to a dozen different rifles tried. My original box of WW brass has had over 30 firings and 4 of them burned through or had a short longitudinal split. I have nearly 1000 45-70 cases and none of them have ever separated.

I have noticed that black powder shooters tend to shoot the tubes off with them leaving the gun or lodging in the bore.
I think this happens with compressed loads and wet chambers. The black powder grains are sharp prisms and have a tendency to grab the case.

If you look at the muzzle of a BPCR in a photo of the powder charge exiting the bore, the power looks like a burning dirt clod. I think this mass of sharp powder grains can pull off the tube when the chamber is wet from wiping.

You might also see this with smokeless loads if you use a filler like cream of wheat or corn meal.

[tygar]

Apples & oranges. 45-70s are not belted.

The belt is where & what cause case seperation. They are headspaced in the belt, therefore greater stress is applied right in front of the belt.

In non straight wall belteds you can chamber the rifle to headspace on the shoulder. This is strictly a custom thing as no manufacturer does other than the belt.

I have one 375 H&H that is headspaced on the shoulder. It works but you should get a custom sizing die to exactly match the chamber.

[blackthorn]

Tygar---you are right of course, but the old Lee Enfield is a rimmed bottle-neck case (no belt) and it is well known to be one of the worst offenders when it comes to case separations. The Enfield's can also be set up to headspace on the shoulder. I suspect the worst offender is cartridge-to-chamber fit when dealing with both rimmed and belted cases.

[EDG]

Apparently you do not really look at how belted cases separate. They separate exactly like any others and it makes no difference if it is rimmed, belted or rim less. Depending on the characteristics of the poor fit between the chamber and the ammo the separations may happen further forward but it is typically about .200 from the junction of the case body and the solid head because there is a combination of both radial and longitudinal stretching at that point.
You will find that a belted case does NOT separate at the front of the belt but rather well in front of the belt. As such it behaves very much like a case with a very small rim since the headspace is also controlled at the rear of the case. There is no reason to discuss headspace on the shoulder since the original post was about a .458 Lott.

I will wager you will never find a case that separates at the belt because the front edge of the belt is behind the weakest part of the case.


http://www.ronterry.com/arms/images/338Head.jpg

168138 168139 http://i338.photobucket.com/albums/n420/joe1944usa/338.jpg


Apples & oranges. 45-70s are not belted.

The belt is where & what cause case seperation. They are headspaced in the belt, therefore greater stress is applied right in front of the belt.

In non straight wall belteds you can chamber the rifle to headspace on the shoulder. This is strictly a custom thing as no manufacturer does other than the belt.

I have one 375 H&H that is headspaced on the shoulder. It works but you should get a custom sizing die to exactly match the chamber.

[leadman]

I have yet to find any brand of 7mm Rem Mag brass that has a belt in spec. I had problems with short case life also but in my case I could headspace off the shoulder to stop this.
Might also check the neck area of the brass and chamber to make sure there is enough clearance to release the bullet/boolit properly. Have run into this using boolits that are matched to an oversized bore with a chamber neck that is on the tight side. My 43 Mauser will not take a boolit larger than .450", while the bore is .457".

[EDG]

You might consider new cutting off new .300 Win Mag brass and using it in your 7mm Mag and head space it on the shoulder.
I have considered using .416 Rem Mag brass in a .375 H&H but I will not do that until my current pile of brass is gone.


I have yet to find any brand of 7mm Rem Mag brass that has a belt in spec. I had problems with short case life also but in my case I could headspace off the shoulder to stop this.
Might also check the neck area of the brass and chamber to make sure there is enough clearance to release the bullet/boolit properly. Have run into this using boolits that are matched to an oversized bore with a chamber neck that is on the tight side. My 43 Mauser will not take a boolit larger than .450", while the bore is .457".

[gnostic]

I make and shoot 6.5 rem mag all the time and haven't seen a case fail from anything other than an enlarged primer pocket. I never FL. size (except for 223, 3030 and 7.62x39) and always seat the bullet into the lands, like I'm fire forming a case. It's always been my understanding, that the size die shouldn't touch the shoulder, or you'll have problems like you're having.

[leadman]

EDG, I fire-form all new brass with 20grs of Unique, fill the rest of the case with Cream of Wheat cereal, and put a wax plug in the neck to hold the contents in until I fire it. Have gotten 5 or more full power loads out of the cases now with setting the die for .001" to .0015" head space. This is in an Encore Pro Hunter so easy to check the head-space on. This is shot mostly for hunting and seldom plink with it so I am satisfied with this.

[EDG]

If you are careful not to over load or stretch it, due to a poor die setting, I have had cases last between 30 and 50 firings with both 45-70 and .222 Rem Mag brass.
The primer pockets eventually wear from pressing so many primers in and out of the cases.


EDG, I fire-form all new brass with 20grs of Unique, fill the rest of the case with Cream of Wheat cereal, and put a wax plug in the neck to hold the contents in until I fire it. Have gotten 5 or more full power loads out of the cases now with setting the die for .001" to .0015" head space. This is in an Encore Pro Hunter so easy to check the head-space on. This is shot mostly for hunting and seldom plink with it so I am satisfied with this.

[rockrat]

Instead of paper shims between the bolt face and case head, I would get a set of feeler gauges and a sharp pair of scissors or some "tin snips" and cut a small piece off different shims to fit in the bolt face. That way you can measure the distance without worrying about the paper compressing and giving a false reading.

[tygar]

Apparently you do not really look at how belted cases separate. They separate exactly like any others and it makes no difference if it is rimmed, belted or rim less. Depending on the characteristics of the poor fit between the chamber and the ammo the separations may happen further forward but it is typically about .200 from the junction of the case body and the solid head because there is a combination of both radial and longitudinal stretching at that point.
You will find that a belted case does NOT separate at the front of the belt but rather well in front of the belt. As such it behaves very much like a case with a very small rim since the headspace is also controlled at the rear of the case. There is no reason to discuss headspace on the shoulder since the original post was about a .458 Lott.

I will wager you will never find a case that separates at the belt because the front edge of the belt is behind the weakest part of the case.


http://www.ronterry.com/arms/images/338Head.jpg

168138 168139 http://i338.photobucket.com/albums/n420/joe1944usa/338.jpg

Well I guess 50+yrs with belts & working with many gunsmiths to make my customs from hunters to 1k guns didn't teach me anything. You must be really smart. I guess my current 15 or 20 or more belteds, & the thousands of cases I process each year, everyone of them that is belt sized & checked with a prick, don't qualify me to comment.

Give me a break. In front of the belt from just in front to about 1/4" & yes I've seen them seperate right in front of the belt.

Everything I said is correct! As far as straight wall the thread opened up a little & other stuff came in.

You can make any statement you want but don't even think about telling me I don't know what I'm talking about. Ahs that nit pick "in front" of the belt to make a little point needs to find something else to do.

[Jedman]

To check your headspace, just fire a sized case with a primer in it. If the primer is above flush with the bottom of the case you have excess headspace or your brass is out of spec.

Jedman