Old Argentine Mauser conversion brass cracking up

Maybe 30 years ago I purchased an Argentine Mauser Model 91 long barreled rifle in military fit, and proceeded to convert various 30-06 brass. Initially I fired a bunch of them with the Hornady 150 and 174 grain 0.312" bullets and used them for deer hunting successfully. Later I converted to shooting reduced loads using lead projectiles and never had any trouble with my converted brass. Recently I found a bag of about 100 of them with the 174 grain J-Bullets and decided to shoot them. I got good accuracy with them but more then half of them resulted in cracks running down from the bullet opening over the entire neck and down past the bevel onto the body by about 1/8". And sometimes there were more than one crack like this on each case. So, what is the problem here and what can I do about it? Or do I need to just throw these away and start over with new brass in this caliber which is available for sale now?

Annealing went south with age it sounds like. The older the case the harder the case gets over time.

Or.......the case was made to short causing the brass to stretch more than normal.

Do you know how many times the brass was fired? Were they ever annealed?

Any chance they were exposed to ammonia fumes while in storage?

the older that brass gets the more it gets brittle and rotten. no surprise!

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Originally Posted by GRUMPA

Annealing went south with age it sounds like. The older the case the harder the case gets over time.

Or.......the case was made to short causing the brass to stretch more than normal.

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Yep...Off the top, I'd think a little of both. Prolly should do a chamber cast to get to the bottom of the problem.
Those split cases could have been sized with a different set of dies than those you are using today...need more info...
Have you ever measured several fired cases from base to the middle of the shoulder with a comparator and contrasted that measurement with that of a sized case?
Work hardened brass has a bad habit of splitting when you move it too much over-sizing.
Never heard of 'old' brass being brittle because of it's age...something had to happen to it...wonder what it was?

Old and/or work hardened will split. I've had some cases on loaded ammo split while sitting in the plastic ammo boxes. No major reforming, just necked down .30 to 7mm. Some old brass does seem to become brittle as it ages. Maybe due to alloy or lack of annealing.

There was a thread a few months ago about factory Winchester silvertip ammo from years back that exhibited splits in the neck. Factory new, but may 30, 40, 50+ years old that had started to split.

A lot of them are Winchester cases, and if I remember all that long ago, I just resized them using Hornady Argentine Mauser reloading dies and trimmed the finished cases to size. Then reloaded them. The cases were probably all once fired before the conversion. And they were sized to press-fit in the chamber of the rifle. And when I fired these they were all tight in the chamber when closing the bolt. I wonder now if I should pull all the J-Word bullets from the remaining 60 or 70 cases and fire the primers off and then anneal the cases and see if that will fix the problem. Or should I just save the bullets and powder and ditch the cases and buy new ones in the correct caliber? Or, should I ditch these and make some new ones with new 30-06 brass and anneal the cases before fire forming with lead projectiles and then use full power lead projectile loads?

That would be the way to go. [smilie=f: Each would likely work. Personally, being the skin flint I am, I would pull the bullets, save the powder, anneal the neck and barely the shoulder, then reload and fire. The neck and shoulder could be annealed with the primers in place.

I would do some checking on the neck diameter. If your the one that converted 06 brass into 8mm you need to ream or turn the necks.

Find a loaded 8mm round and measure the neck, do the same with 1 of your conversions, note the difference in diameter.

When I do those I have to ream the necks for them to work.

I have 6 of these rifles and have converted a lot of 30-06 based brass to the 7.65X53 Arg. brass over the last 30 years. The brass has not needed neck turning or reaming as the military chambers on the 1891 Arg. rifles is fairly large in the neck with a long leade.
I think the brass is just old causing the splitting. Since the chamber could be damaged by gas leakage cutting into the metal I would hunt up some new or recently made once fired to convert. The PPU brass seems to be pretty good and is relatively cheap compared to Norma or Hornady.

Last night I broke down all of the remaining loaded/converted cartridges and think that maybe I will just throw all of them away and start over again or purchase some new PPU brass from Grafs. I enjoy all the time in the reloading room converting the 30-06 brass but to buy new 30-06 brass and then convert it rather than just purchasing the 7.65x53 Argentine brass for the same money just doesn't make much sense. I am not even sure I will bother trying to anneal this old brass. Too much of a chance of damaging one of my favorite rifles with this old stuff. But what should I do with all of these 174 grain Hornady round nosed jacketed projectiles since I usually use a 314299 cast with good results in this rifle? Or should I save them for maybe Grizzly Bear or Moose just in case I ever get a hunt of a lifetime?

I believe that your thinking on this is sound. Why convert .30-06 when you can get new 7.65mm brass? As for the 174 gr. Hornady bullets, they're an outstanding choice for .303 British, and will work in 7.7 Jap.

I've done the '06-7.65 mm conversion many times (but not for about 20 years) and after knocking out the old primers the very first thing I'd do would be to anneal them by standing the cases in a baking pan with water about 2/3 of the way up the body of the case. I'd hit each one individually with a hand held propane torch until it was a bright orange, then stick a short piece of welding rod into the mouth and tip it over into the water. Next step, running it into a 7.65 mm sizing die, the brass formed very easily. I've never experienced the neck cracking you describe, but I've probably never reloaded any one box of cases more than 3 times. Probably right around then would be a good time to re-anneal.

I’ve had brass split like that before. I loaded some old 30-06 brass 25+ years ago. It was old then but I didn’t know about annealing back then. When I dug it out a few years back a lot of them had little neck cracks. Now that I anneal I don’t see those problems at all anymore.

As to neck cracks damaging guns, I’ve never seen that myself. Not saying it can’t happen; I’ve just never noticed a problem. So long as the crack doesn’t extend very low on the case body I’ve always considered them relatively benign, though I avoid knowingly shooting cracked cases.

If it were me, I’d just anneal the ones that don’t have cracks, though personally I wouldn’t be comfortable with annealing brass with a live primer. I would expect they’d be quite safe to use, especially with light loads.

On the other hand, new brass in old military calibers is so available and affordable nowadays that that’s not a bad way to go either. There’s definitely something to be said for having nice new brass all with the correct head stamp.

I had the same problem years ago and anealing the shoulders and necks fixed it.

I never pass an opportunity to discuss my mis-hap fire forming brass in a 91 Argie. The 91's do not have the vent for gas sneaking by the shoulder. Had one blow back into my face and literally fried the right lens of my shooting glasses. If I didn't have the glasses on it would have been my eyeball that was fried. Most of us know to use shooting glasses and hearing protection but as I'm sure many of the ol'timers can tell you. Neither wasn't all that common back in the early 70's. I thought in my early 20's I was invincible. Had I not got the shooting glasses as a free-be in a promotion. Chances are good it would have been my right eye that got the hot blast of burning powder.

I have had 223 brass do the neck split thing while sitting loaded in my gun room. It had been loaded approx. 10 years. I do no remember how many times it had been loaded.

If you plan to buy new brass, just get it in the right caliber with the correct headstamp. Anneal after three or four reloads.

If using range pick-up brass, anneal before resizing. My experience with 1891 and 1909 Argentine Mausers showed that with cases made from 30/06 brass the necks were never too thick, and I made cases from 7 and 8mm Mauser, 270 and 30/06 cases.

I used cast 311299 as well as Sierra 150 and 180 jacketed.

As for seeing damage done by a neck crack it would be very difficult to see without a bore scope. I recently purchased the Lyman bore scope and was astounded to find some of my barrels that looked good with the eye actually had pitting, rough machine marks, etc. Most shoot just fine, a couple would not and that is why I bought the bore scope.
Good decision to buy the proper brass and move on.

I've formed a lot of 7.65 Argentine from US milsurp cases back when commercial brass hard difficult to find and expensive. Had the same problem the OP has with necks splitting as the cases grew older. Annealing the necks and shoulders solved the problem. I also formed quite a bit from commercial 8x57 cases. Never had had the splitting problem with them as the newly formed shoulder and neck never got below the annealed portion of the original case.

Anneal but not with the primers. I have removed live primers many times and just did 200 last week. (problem with rifle)
I just purchased a Lee decapping die and it has a lot of room around the outside of the case to direct gases down if one should go off. I have never had one go off on me, though. I will reuse those primers, too. The reason I took them out was to re-anneal the cases not knowing the barrel on the rifle was junk. (no rifling left) Make sure to wear eye protection, just in case.

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Originally Posted by toot

the older that brass gets the more it gets brittle and rotten. no surprise!

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Oddly enough, I have a bunch of old Nazi made 8x56mmR and have yet to have one crack or split. Seems likes it's still good enough to go through the trouble of converting it to boxer primers so that it can be reloaded.

After "unloading" the Argentine Mauser brass that had been converted from 30-06 brass 30 years ago, I inspected all of them and discovered that more than half of them had cracks about 1/2" down the case from the mouth down over the shoulder. So all of them went in the trash and I am ordering new, real Argentine Mauser brass with boxer primers and start over again. Next time I do a conversion like this I will anneal the cases before the first time I load them. And I better go back and check all of those other converted cases I am using. Although now days I shoot mostly low pressure lead projectile loads in them and just go to bigger calibers for deer hunting and leave these small caliber lead bullet guns for target shooting. Especially those Swedish Mausers!

Instead of the trash can, sell to a recycling center or melt them and cast into useful items such as muzzle loader furniture.

With that many cracks, I can't blame you for just scrapping them all.

Just yesterday I bought several boxes of .45 Colt: someone else's reloads from the 1970's. They were cheap, component value. I just got done pulling them all down. They were all clearly labeled, so now I have a bunch of primed brass, half a pound of Unique, and a few pounds of cast bullets to recycle into new cast bullets.

A couple of the boxes turned out to be unfired brass, one was marked as twice fired, and another thrice fired. On the thrice fired ones some of them pulled too easy so I looked and about a dozen of them had cracked necks, just from sitting.

I think that brass that is a bit hardened from repeated firing or reforming without annealing just can't take the neck tension over the years. I assume they probably would have been fine 40 years ago.