How much pressure to do this???

jonk

Once upon a time when younger and dumber, I got a big canister of 8mm Mauser ammo. It fired fine- when it fired- with no pressure signs. The problem was, about 40% were duds or hangfires. It was FN Belgian ammo from '49.

Soooo... with nice projectiles on one hand and powder that looked fine and worked well in those that went off in the other, I got the idea to reload the components in a fresh case with fresh primers. Ok idea, and I'd done it before with no problem.

Well whatever caused it, be it smaller case volume, hotter primers, etc., the new case and the old components were a bad mix. I had several cases strech notably, primer pockets leak to the point that the primer just fell out when I opened the bolt (never mind reusing it!) and a very noticablely heavier recoil.

Now, the normal spec on the 8mm Mauser is that it develops somewhere in the range of 47k psi (as I recall). With such a pressure level, I usually split a neck before I enlarge a primer pocket, but it takes 10, 12, 15 loadings at max book loads to reach that point for me with winchester brass. So, what sort of pressure levels would open up a primer pocket with ONE shot? The brass did not fail, nor was the gun damaged- I checked it with my field gauge after said 'boom'. The 98 can handle up to 100,000 psi if forced to, and I gotta think that that cartridge was up there....but where?

On another note, I tried downloading the pulled powder and worked up to a safe load, about 5 grains shy of the original loading.

tsavo303

I bet the newer primers were much faster and hotter.
Have no idea on pressures

JustC

sounds more like excessive headspace to me. It sounds as though the case was driven forward upon firing pin strike, and upon ignition, it slams back against the boltface creating your greater perceived recoil from increased bolt thrust. During this time, the primer is backing out of the pocket, until it is slammed back against the boltface reseating it. However, the oversized chamber has allowed the case to stretch to the chambers dimensions, which will increase the size of the primer pocket as well as weakening the case-head area.

also,..remember that as powder ages,..and especially if it is subjected to multiple travels during it's lifetime, the coatings deteriorate and the grains will be broken or fractured. This INCREASES burn rate, which in essence, changes your load to a load of faster powder.

was the bolt lift stiff?? was the primer pierced?? Primers cratered?? If not,..I am going with excess headspace and old powder.

Tailgunner1954

Normaly you can figure that it takes about 75K to stretch the pocket, but that can vary depending on how loose the chamber diameter is (room to expand), how hard the brass in the head is (what it takes to make it flow) and how thick the head is (amount of material to move).

You can test the internal volume with water (weigh a primed case, fill with water and re-weigh. Subtract the empty weight from the full weight). It might also be interesting to take a hacksaw to some of the mil-surp and Win brass.

The neck spliting comes from the brass becoming work hardened in the firing/reloading cycle, and has nothing to do with pressure (vs stretching of the web at the base of the case)

jonk

The gun has excellant headspace.

I am an experienced reloader and fully understand the difference between chamber headspace vs. cartridge dimensions, which isn't to say that I couldn't have slipped on one or two, but not on a whole batch. Point is, it was once or twice fired brass, from that gun, and necksized only. No headspace problems. 100% guaranteed.

Bolt lift was very stiff. Primers were not cratered or pierced, but well flattened and singed at the edges for lack of a better term.

I did check the volume of the two; and they were very close but the milsurp cases were actually smaller in volume, which leads to further puzzlement.

But, I got my question answered; roughly 75,000psi.... yow, amazing that simply transferring components could make such a difference! And good to know that the old 98/22 can still take a nearly proof power load- though I don't plan on repeating the experiment!

JustC

Then depending on the factory spec burn rate for that powder,..I am going with older powder becoming deteriorated. I have seen this first hand. I went the first day of a 2 day varmint class match last summer,..and was running my VSSF in 220 swift with RL15 in factory class. I managed to secure 1st place at the end of day 1,..so naturaly I had to show up for day 2. I get home to load my rounds,..and I don't have enough powder to make enough rounds to run sighters and match rounds. I have to either let it go,..or find some powder on Saturday night so I can show up tomorrow. I call Bill Truit www.billsaccuracy.com and he says he will leave an old can he found in the shop on his tailgate. I pick up the powder and come home to load up for tomorrow. I mix the remaining powder of mine, with his old can, so as to at least uniform it all. I go to the match tomorrow with higher velocity and less accuracy.

Point being,..the older powder, was significantly faster than my new can was.

never doubted your loading prowess[;)] just wondered if this was an old rifle that your tinkering with.

let me ask this,..you pulled bullets and powder from military cases right?? and loaded it in american brass right?? and I have always found military brass to be thicker than american brass, thus less volume. If you were to run a vloume test and find the military brass to be less than your winchester brass, then it has to be the powder.

I'd be interested to know what the culprit is.

jonk

I would imagine you are right, that it had to be the powder. The combo of obviously anemic and degraded primers and somewhat faster powder due to age and deterioration TOGETHER were ok, but couple that degraded, faster powder with new primers and it meant....well not disaster for a nice 98 action and 2 or 3 shots, but it could have led there with repeated firings. The strange thing was, the powder looked and smelled fine- no brown dust in it, no foul smell, no corroded bullet bases.

I might risk capping off one more of the overloads via a string through a chronograph to see how fast they are moving, compared to the original hit or miss stuff. If the first 3 overloads didn't even move headspace, I doubt the fourth would hurt anything either and it would be interesting to find out.

scubabobf

Jonk;
I question the wisedom of continuing with a dangerous mixture. Does the info lead to any decision? If not there is little value in continuing. It is good to be inquisitive but with a purpose and always do a risk reward evaluation. I see great risk and scant reward in continuing. Good luck.