Dies for my unknown 8mm

[swampcrawler]

A while back I put up a post trying to figure out what this little fella is, but no one can find any known cartridge that exactly matches it. It's basically an 8mm-06 but with the shoulder moved forward maybe a quarter inch and a short neck.



from left to right: 8x57, chamber cast, Fireformed case, 30-06.

It seems hornady will make me a custom die set for around $170, but I was wondering if it would be possible to load for it with maybe a 8mm-06 or 8x57 neck sizing and bullet seating die? Or is dishing out the cash and waiting on custom dies the only option?

 

[Vern Humphrey]

You should have no problem. (I say that without measuring the casting, and assuming your assessment of what you have is correct.)

The shoulder angle seems unchanged -- and that means a properly-adjusted 8X57 die should be able to push back the shoulder every few reloads, if it gets hard to chamber.

 

[ironworkerwill]

Good luck on the 8x06 imp? You could get maybe 2 Lee fl dies, bore the shoulder out of the first die to resize closer the base, use a 8mm-06 die for the top end? I think it's do- able, DIY even.

 

[fguffey]

no one can find any known cartridge that exactly matches it

Not often but I cast chambers, I do not have any of the bad habits others use. When I cast a chamber, I cast the chamber.

The 8mm06 case body has the same dimensions as the 30/06 chamber/case diminutions. Meaning there would be no artifact of the case body/shoulder juncture on the fire formed case. On the case (second from right) the artifact of the 30/06 case body/shoulder juncture is visible meaning the case body length on your chamber/case is longer than an 8mm06.

Point? I built a 338/280 Remington, I could have built a 338/06 with the shorter case body but chose the 280 because of the longer case body. The case body for the 280 is .051" longer than the 30/06 case body. I could have used 30/06 cases but when fire formed the case would have shortened when the case filled the chamber. It only happens to me but when forming first and then fire forming I have cases shorten as much as .040" from the mouth of the case to the head of the case.

Your claim of .125" difference and describing it as 'about, near or close to' does not help me. A reloader with a good understanding of 'datumn' can measure the length of a case in absolute numbers.

Absolute numbers and distances: I would measure the length of the case from the datum to the head of a fire formed case first then I would adjust the die off the shell holder that amount. If you are correct and your guess of .125" adjust the die off the shell holder .125".

I purchased two sets of dies for $11.00 each, one was a 338 Magnum and the other was a 280 Remington die set. Between the two I managed to load the 338/280 cases.

My plan was to go to 338/280 Improved.

F. Guffey

 

[Jim Watson]

I think you can flange up something that will work without paying for custom dies.

It would take very careful measurement of a very good cast or a fully fireformed case to tell whether you had the 20 degree Mauser shoulder or the 17 degree '06 shoulder.
But does it matter a whole lot?
I think I'd try the 8x57 dies.

You also need parts to let you do the old expand up, size down trick to get a false shoulder for the fireform shot. Or you could use the Rocky Gibbs technique of a bullet seated out to jam into the lands and position the case head against the bolt face. The latter only if you have a chamber throat and lede short enough to have a bullet reach all that way.

 

[swampcrawler]

Crud. I had completely forgotten about the need for a false shoulder.....
To form these cases I just loaded in a little unique, filled case with cream of wheat, stuffed a piece of tissue in the mouth and fired them. The extractor held them enough for the primer to detonate but I now see that isn't the best way to go about this.

I'm still new to bottleneck cartridges...

 

[Jim Watson]

That can work.
Cheaper than buying a tapered expander die or blowing away a bullet just to fireform.

.30-06 brass is common and relatively cheap. You can experiment.

 

[Vern Humphrey]

I make .35 Brown-Whelen cases by charging a .30-06 case with a little Bullseye and a quarter sheet of toilet paper, then feeding the case through the magazine and firing.

My rifle is a custom '03 Springfield, and the extractor holds the case against the bolt face and everything comes out nice.

 

[swampcrawler]

Ok. That makes me feel better. Well I bought some h4895, some 125 (they were cheap. Not real sure what they will be good for) hornady soft points and 150 gr Sierra pro hunters and hornady interlocks. Just need dies now.

 

[frankenstein406]

I think lee charges $70