8mm Mauser JS

[AmbulanceDriver]

Ok. So I recently started reloading for my Yugo M48 Mauser, and am looking for the opinion of the learned folk here at THR. I'm a bit concerned about possible high pressure signs in this brass.

First, here is the load I'm using:

Rem Brass
Hornady 150GR SP bullet
47 gr of Accurate 2015 (max load per manual, happens to be most accurate)
CCI 250 primers (large rifle magnum)
Seated slightly long at 2.950" (instead of the min 2.940" listed)

This is the load listed in the Accurate 2004 loading manual.

Here's what I'm seeing on the brass that causes concerns. Vertical lines appear on the brass after firing. Some of them are apparently being caused by the bolt moving across the top of the brass, others may be due to burrs in the chamber. Included are a couple of pictures of the brass.

Also, ALL my primers are flattened. No primer flow, no cratering around the firing pin impression, but I've also heard that the chambers on these rifles can be a little loose, maybe contributing to the flattened primer?

Finally, the brass were all trimmed to 2.230". Not much stretching going on, many only 1-2 thousandths, a few as far as 5 thousandths, but no more than that.

Am I good with this load, or do I need to try to find a combination that has lower pressure while maintaining accuracy?

 

[brentwal]

loose the Magnum primers, that maybe the cause.

 

[brentwal]

Newer Accurate load data, no Hornady 150gr., but they are showing only using WLR primers no LRM.

You may want to switch to 2460 or 2520, both of those powders are better suited to the 8x57mm Mauser.

 

[Afy]

Drop the charge...by a grain or two as well.

 

[rcmodel]

The parallel scratch lines have nothing at all to do with pressure.
They are getting scratched by rough feed rails in the receiver.
Polish the rails, and the scratches will likely go away.

The horizontal rings up near the shoulder are caused by a rough chamber, with reamer marks still present.
Again, nothing at all to do with excess pressure.

I can't comment much on your load, but Magnum primers would not be my first choice for the 8mm Mauser.
However, since that is the primer Accurate lists in the load data, that is what you should use.

If you are not getting loose primer pockets after two or three loadings, I'd say you have found a perfectly fine & safe load.

rcmodel

 

[NCsmitty]

rcmodel, has it right, you're getting feeding scratches. 2015 is a little fast burning for the round but the smoking half way down the neck indicates a good load to me. As long as the smoke line does not extend into the shoulder area.(lower pressure or bad chamber) Original Turkish milsurp powders used in the 8MM were near IMR3031 in burn rate and they were for the most part, pretty hot loads. If you are getting good accuracy and the cases extract ok, keep on shooting. If you go to a heavier bullet though, I would use a slower burning powder.

NCsmitty

 

[Der Verge]

I have had primers flatten in factory ammo in my X57. If the bolt is not hard to turn open, well, not any harder then normal, I would not worry about it. Well, I would worry if it were 40 degrees out today, and you were going to go shoot the load in the desert next summer......

 

[AmbulanceDriver]

I appreciate the feedback. I suspected that the scratches, etc. I was seeing were from feed rails/bolt/chamber, and not necessarily pressure signs. Primer pockets are all still nice and tight. This is the third loading for these particular cases, and so far so good. I plan on switching to neck sizing only (only have one rifle in this caliber) before my next loading to minimize work hardening. Any suggestions on cleaning up the chamber? Should I even bother?

The bolt turns easily, they extract with no problem. This load is pretty accurate in the rifle, I'm gonna look at my targets from my last couple range trips, I think the load just below this one was pretty close in accuracy (0.3gr lighter).

I'm pretty happy with this load, I'm thinking it might end up being a hunting load for deer, maybe even elk here in OR... MV was around 2900fps, so it's a pretty smoking load.... It'll be good for eastern OR....

 

[rcmodel]

Any suggestions on cleaning up the chamber? Should I even bother?

At most, I would give it a light polishing with 400 or finer black Wet or Dry emory paper wrapped around a wooden dowel rod.

But the reamer marks are really not hurting anything if the cases extract normally.

rcmodel

 

[AmbulanceDriver]

Yeah, I wasn't sure if I needed to worry too much about the chamber. I'll try the same treatment on the feed rails though, because I have had a couple problems with feeding reliability, just clean up the magazine area in general.

 

[ForneyRider]

Varget is a good powder for 8x57. I loaded some with 150gr Sierras and CCI large rifle magnum primers. Trajectory is much flatter than a typical 196gr bullet.

8x57 JS is high pressure military cartridge, but a lot of load data is suitable to older versions of the 8x57 rifle. IMHO, it is basically a .30-06 with .323 bullet and slightly less powder capacity(case is shorter than .30-06).

 

[Sunray]

"...max load per manual..." Did you work up to that or just pick it? If you picked it, that's not a good idea. Not unsafe, but it isn't necessarily the most accurate load.
"...plan on switching to neck sizing only..." You'll have to work the load up again. I'd lose the magnum primers too. You don't need 'em.

 

[ForneyRider]

Handloader Journal (Sept 08) had an article on WWII guns. He loaded up the 8mm Mauser with 195gr and 200gr bullets with 48gr of Varget.