How can I reload for my mystery 8mm?

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swampcrawler

swampcrawler

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Some of you probably saw my thread in rifle country about this. Basically I bought a nice old sporterized k98, fired an 8×57 through it, and this happened.

20140927_150232.jpg

So i fire formed a 30-06 in it.

20140927_164835.jpg

left to right is 30-06, fire formed mystery round, 8x57, original attempt at firing 8x57.

I cannot for the life of me figure out what this is.

It's an 8mm Gibbs without the steep shoulder.

It's an 8x64s with the shoulder blown a hair too far forward.

It's an 8mm-06 with the shoulder like 3 mm too far forward.

It's a... something.

So sense I can't figure out exactly what it is but have identified the general neighborhood, I'm thinking maybe with 8x57 dies and maybe some other stuff I can put together some rounds for it?

How would one go about something like this?

This is absolutely driving me insane. Hopefully you guys can help out. If nothing else, what could it be reamed to? There's not much left to go to with the shoulder cut so far forward... :banghead:
 
It's a "yep" I would go with a low pressure load you know is safe and build up. Start at maybe 30-30 loads and go up until you get nice tight groups.
 
That's what I was thinking... start with nice soft loads and very carefully work up.

My main concern is not knowing which dies to use to resize, seat and crimp. I'm not sure how much play those dies have in them.
 
Did you at least check the bore for obstructions before you fired it with improper ammunition?

Cerrosafe is your friend and its use makes a lot more sense than sticking ammo in it that looks "close enough" and touching off 50,000 psi or more just inches from your face. The .318" I bore size was still made and used in civilian rifles at least up until WWII.

What if someone had chambered your rifle for a wildcat 8x55I Swiss with its much larger case diameter and a .318" bore?

Cerrosafe is cheap and reusable, I've been using the same half pound for at least 15 years.

It's a whole lot cheaper than a new rifle and WAY cheaper than facial reconstructive surgery (unfortunately, new eyeballs are unavailable at any price).
 
Yes I did manage to check the bore for obstruction. Along with a complete tear down, inspection and cleaning of the rifle. In my mind the nazi marked mauser 98 sporting it's original, numbers matching barrel had no business being anything but 8x57. In the future I will include chamber casts in my new gun inspections.

Now, any answers to the questions above rather than unneeded and somewhat insulting lectures?
 
Perhaps I should have been a bit more clear in my earlier posts...

I'm not just guessing here. After the first round that didn't go so well, I fire formed that '06 case, and then did a chamber cast. I didn't want to wait on cerosafe to get delivered so I did it the old way with sulfur. Worked just fine. The cast matched my casing perfectly, and I have compared the dimensions to every 8mm cartridge I can find and it does not match any of them.

20140928_181243.jpg

8x64 s Breneke,
8mm-06
8mm-06 improved
8mm gibbs,
8x64 RwS
8X63 swede
7.92x61 Norwegian long

It doesn't exactly match any of them. It's close to several of them, but not exact...

What I'm trying to find out here is, sense I can't find a known cartridge that matches this perfectly, how could I go about loading for it?

Someone mentioned it would probably be possible to lead it with backed off 8x57 dies. Would that be possible or should I send a chamber cast to a die manufacturer and have an appropriate set made for half the cost of the rifle?
 
If the shoulder angle works and the shoulder diameter of your fired cases isn't a whole lot larger, you can probably get by with partial neck sizing them in an 8x57mm die, assuming that your chamber is reasonably smooth and you don't push pressures too high.

My apologies if I offended you in my first post, but if you'd included some of the information that you put in your last one, I probably wouldn't have made some of the (admittedly negative) assumptions that I did.

Us swamp folks iz gettin' rare enuff wiffout lettin' any uv our kind blow thereselfs inta gator bait! :)
 
No problem swamp man. Totally understandable!

That's a possibility that makes some sense to me. Someone ran an 8mm06 reamer in too deep by mistake or maybe just to squeeze out a little more case volume.
 
case forming without firing:

How would one go about something like this?
Click to expand...

I do not know about One, I only know about me, I would start with a 280 Remington case, I have 280 Remington cases necked up to 35 Whelen and 338/06, 100 each. There is a very good change I will never use the cases but JIC, as in 'just in case' I need to determine the dimensions of a chamber I have the cases and it is not necessary for me to leave the shop, nor is it necessary to fire the cases.

I have fired 8mm57 cases in an 8mm/06 chamber, the fired cases came out looking like a 30/06 case with a very short neck. Your formed 8mm57 case has only a hint of a shoulder, the neck length of the Gibbs is close to .217". the short neck is the reason I use 280 Remington cases, the 280 case is .041" longer than the 30/06 and the shoulder is forward by .051".

I do not see where you measured the diameter of the case at the case body/shoulder juncture, your formed case looks larger in diameter than the 30/06 meaning the chamber is improved with less body tapper and there is an artifact left by the old shoulder, reloaders believe the shoulder moves by bumping? Your shoulder did not move, it was erased, the shoulder on your formed case is new and was formed when the case formed to the chamber.

Problem? The artifact could be from the old case body/shoulder juncture and the beginning of case insipient separation, check the inside of the case. Point? Head space: I have fired many cases with a difference in length between the case from the shoulder to the head of the case and the chamber from the shoulder and bolt face of .127" without the case stretching between the case head and case body. Proof? The artifact left on the formed case, your shoulder did not move meaning the case did not move forward, had the case moved forward when the trigger was pulled the case would have locked to the chamber forcing the case to stretch back to the bolt face. We should all know a case wi8ll not stretch .127" between the case head and case body.

What you did is the reason I form cases by necking up 280 Remington cases, I also neck up 30/06 cases to 35 Whelen and 338/06 cases. Again, I have no fewer than 100 each in 35 Whelen and 338/06. When checking the length of a 30/06 chamber I want to know the length in thousandths, I form cases to fit starting with a case that is too long from the shoulder to the bolt face then adjust the die to reduce the length of the case from the shoulder to the case head until one chambers, yes, I could use one case but that would cause me to start over the next day.

I have dies, Gibbs, Wildcats, Ackley, etc. My favorite die is the short fat case body dies. the 308 W is my favorite, then the 243 W, after that the 350 Remington mag die. I have forming dies. If I had your chamber I would start with 280 Remington cases necked up to 338/06, I would use the 308 W forming die to size the case neck down and establish a shoulder, to establish the shoulder I would adjust the die off the shell holder .890" because that is the difference in length from the shoulder of the 308W to the case head and the 30 Gibbs from the shoulder to the case head. I would use the 308 W die because the case body is larger in diameter than the 30/06 case body.

There is chamber casting, problem, One and I do not do it the same way.

F. Guffey
 
No problem swamp man. Totally understandable!

That's a possibility that makes some sense to me. Someone ran an 8mm06 reamer in too deep by mistake or maybe just to squeeze out a little more case volume.
Click to expand...

No, not possible, if it was as that simple the length of the neck would be the same length as the length of the neck on the reamer. Then there is determining the length of the chamber from the mouth of the chamber to the bolt face, a case forming reloader can form cases that determine the length of the chamber.


F. Guffey
 
Someone mentioned it would probably be possible to lead it with backed off 8x57 dies.
Click to expand...

You have all the information you should have to back the die off the shell holder when forming cases. If you had the ability to measure the length of the fire formed case from the datum (.375" diameter) to the head of the case you could use a 8mm06 sizer die, subtract the length of the 8mm06 case length from the datum to the case head from the length of the formed case from the datum to the case4 head. the difference in case length between the two should tell you how far to adjust the die off the shell holder.

then there is the absolute, you have a chamber in the rifle, after making an attempt at forming chamber the formed case. I would not worry if I did not have all the 8mm sizer/forming dies.

You want to know the length of the chamber from the shoulder to the bolt face.

What to do about the unknown, someone said you can not load for this chambering, I do, I would. I would use the maximum load for the 8mm06 as the starting load.
F. Guffey
 
8x68 is the most logiical cartridge but really big but. thats a big game rifle, ive seen commercial loads that push 4000 footpounds at the muzzle.

if you want to reload and do it in a way that will be the least agravating....

anneal a few 30-06 cases, put a typical fire forming chargein them, fire a dozen off. then call up Hornady and talk to their customer support team and send hornady the fire formed casings AND the chamber cast.
Send a check along and they will MAKE you a set of reloading dies. Ideally they want the chamber reamer/chamber drawings, but the cast and a dozen fire formed cases should be enough.


other wise

1. anneal 30-06 cases
2. fire form cases to chamber
3. NECK SIZE only
 
Hmm.

I never would have imagined this thing would be so difficult to pin down. Thanks for all the info so far!

Case dimensions are as follows. Give or take a couple thousandths.

Base to shoulder: 2.1
Length of shoulder: .15
OD near base: .466
OD near shoulder: .442
Length of neck: .238
Case length is 2.494

That makes it nearly identical to the gibbs except it lacks the sharp shoulder angle. I don't know how to measure it but it seems nearly the same as the 06...

Bezoar said it would be possible to neck size Fireformed cases...

With what die? An 8mm06?
 
With what die? An 8mm06?
Click to expand...

Because:

Bezoar said it would be possible to neck size Fireformed cases...
Click to expand...

Before that F. Guffey said you could use a 308 W full length sizer die because it is larger in diameter like a neck sizing die, but, a problem, learning to adjust the die off the shell holder and then 'by how much'. Then there is the 8mm338 mag die for neck sizing.

Next? Measuring the length of the case from the shoulder/datum to the head of the case,

Length of neck: .238
Click to expand...

Then someone said the Gibbs had a short neck, the 30 Gibbs has a neck length of .217". As the diameter of the bore decreases the neck shortens, the 30 Gibbs is smaller in diameter than the 8mm meaning as the diameter of the bore increases the neck lengthens.

F. Guffey
 
And then someone suggested it could be an 8mm64 s Breneke.


8x64 s Breneke,
Click to expand...

The 8mm64 has a neck length of .335 and a case length of 2.657". That would make it a good candidate for cylinder brass.

http://www.z-hat.com/Cylinder.htm

Straight wall cylinder brass has a case length of 2.650 and as the advertisement says the case head on the R-P cylinder brass is 35 WHELEN.

F. Guffey
 
I would fire form a few 30-06 cases, make a durable chamber cast, and send em off to Lee or (insert favorite die brand here).

From Lee's website

"A Custom Collet Die set consists of the Collet Neck sizing die, the Easy Adjust Dead Length Bullet Seating die and shell holder. The cost is $70.00 per set plus $6.00 for Shipping & Handling. Maximum outer diameter at the base is .555 and the maximum bullet diameter is .375. There are a few exceptions for the larger Ultra Mags, if you are interested in those , you may want to give us a call or send a case to determine whether or not we can make them. The Collet Neck Sizing Die is not recommended for Auto Loaders, Slide or Lever Action Guns.

If you are interested in a custom Collet die set, send payment $76.00 and two fired cases from the rifle that the ammunition is to be reloaded for, as well as a sample bullet. Please see listing below for cartridges we can not make. The cases are used to determine the dimensions of the dies to be made, the bullet is so we can test the dies before shipment. When ordering Custom dies, we match the configuration of your rifle chamber. The dies we make are hand made to match your chamber. Current lead time for a Custom Collet die set is a 2 months.

Please order online and mail 2 fired cases and sample bullet to:
Lee Precision, Inc.
4275 Highway "U"
Hartford, WI 53027 "




In my opinion, this is the best answer, as then you will have dies to match the rifle EXACTLY, and won't have to sweat trying to get the perfect adjustment on a die set not made for your cartridge
 
In my opinion, this is the best answer, as then you will have dies to match the rifle EXACTLY, and won't have to sweat trying to get the perfect adjustment on a die set not made for your cartridge
Steve2md is offline Report Post
Click to expand...

My opinion? There is nothing wrong with a reloader knowing methods and techniques, step away from the keyboard, there is more to reloading than bumping the shoulder back .002". I am the fan of knowing the length of the chamber before I pull the trigger. there is a good chance the case is too short before the trigger is pulled.

Short as in between the shoulder and bolt face, if you will read this thread over and over and over you will realize that is exactly what happened. I know the firing pin struck the primer.

F. Guffey
 
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