Pressure or Primer ?

[RPRNY]

I have never seen this with a primer in a black powder cartridge.

Rifle is a late 1870s Mauserbuchsen, a scaled down 1871 Gewehr action.

Cartridge is 9.5x47R, an early German adaptation of the 11.15x60R cartridge.

Load was 50grs OE 1.5fg under a 250 grs paper patched slick.

Primer is CCI large pistol.

25 rounds in the same batch, only this one had back flow into the firing pin aperture of the bolt.

As per above, I have never seen what I would normally associate with an overpressure event in a black powder cartridge. And the fact that it was only one out 25 loaded at the same time suggests a soft primer rather than a pressure issue per se. Can’t get much more than 55 grs into the case even under compression, so there’s no double charge at issue.

Your thoughts?

[GARD72977]

That does not look like high pressure. Its likley a set back primer from low pressure

[Kenny Wasserburger]

Or a headspace issue.
KW

[ascast]

I go with set back and headspace issue, otherwise we would not be looking at it

[RPRNY]

We can rule out headspace given that this is one primer out hundreds rounds fired by me in this rifle.

Low pressure makes a lot more sense though why it would appear in only one cartridge is odd. Loose primer pocket?

[samari46]

I'm guessing here, but aren't primer cups stamped much like bullet jackets?. If so maybe you got one that might have had too much force in the stamping making it thinner and weaker as well. Frank

[sharps4590]

I can't answer your question RPR, however. I shoot a 10.5 X 47R in a Jost & Diehl combination gun and I've never seen that kind of reaction. I too would be a lot more suspicious of the primer than the firearm.

[dirtball]

Was this the last round in the string, or in the middle of the string? If it was the last round I would look at the firing pin spring. If it was in the middle of the string and none of the others looked like this it was probably a bad primer. But I would still look at the flash holes in all of the cases for variations, a large flash hole may have allowed a bunch of powder to get into the primer pocket, or a really small flash hole may have allowed the pressure from the primer to cause this. In any case I would mark that case and see if it reoccurs.

Dave

[Gunlaker]

I would try rifle primers. I have a Borchardt and a highwall with original large diameter firing pins and if I use pistol primers there is always a little bit of flow back on the primer, although not quite like in your picture.

Chris.

[RPRNY]

Was this the last round in the string, or in the middle of the string? If it was the last round I would look at the firing pin spring. If it was in the middle of the string and none of the others looked like this it was probably a bad primer. But I would still look at the flash holes in all of the cases for variations, a large flash hole may have allowed a bunch of powder to get into the primer pocket, or a really small flash hole may have allowed the pressure from the primer to cause this. In any case I would mark that case and see if it reoccurs.

Dave

Somewhere in the front half of the string. Good tip, thanks. Bertram brass so worth checking each.

[RPRNY]

I would try rifle primers. I have a Borchardt and a highwall with original large diameter firing pins and if I use pistol primers there is always a little bit of flow back on the primer, although not quite like in your picture.

Chris.

Makes sense too, thanks.

[414gates]

I would try rifle primers..

+1

Pistol primers are rated for pistol pressures.

[RPRNY]

+1

Pistol primers are rated for pistol pressures.

Of course.

What are all of us using pistol primers in 45-70 black powder cartridges thinking?!
What pressure would you guesstimate a 50grs load of 1.5fg black powder in a .375 bore? Much above 25kpsi? Probably not.

[dirtball]

SAAMI spec for 44 Mag 36,000 PSI, 45 Auto 21,000 PSI, 45-70 Smokeless load 28,000 PSI
Pistol Primers should not protrude as in the above pics with a BP load.

Dave

[414gates]

Of course.

What are all of us using pistol primers in 45-70 black powder cartridges thinking?!
What pressure would you guesstimate a 50grs load of 1.5fg black powder in a .375 bore? Much above 25kpsi? Probably not.

I've never loaded black powder, so I don't know what should or should not be done.

The OP said pistol primers were used. The cartridge is for a rifle.

The consensus of what the pressure actually is, is a best guess.

The only variable in the equation is the primer.

It doesn't hurt the OP to use a rifle primer and see if it happens again.

It's not like the bolt face magically opened a bigger hole around the firing pin for that one shot.

[sharps4590]

Ahhh...I missed the part about it being pistol primers. Original BP rifles have larger firing pins and consequently larger holes than smokeless firearms. Go to LR primers and I bet you never see it again. I use LR Magnum primers in all my BPC rifles. That's how I started 40 years ago and haven't found a reason to permanently change.

[RPRNY]

The pistol vs rifle primers in BPCR debate is as productive as discussing religion on the Shankill rd in Belfast…

Appreciate the input. Thanks all. Given this is the first incident of primer flow back of about 560 rounds fired by me in this rifle, all using pistol primers, it certainly appears (and would bear out other concerns around Bertram brass) that brass issues, from enlarged flash hole to loose primer pocket, are leading contenders that bear investigation, or a soft primer.

[Gunlaker]

Generally pistol primers are fine for black powder loads. I use them even in loads for the .45-2.6 with 100+ grains of powder. But in rifles with original large diameter firing pins they sometimes seem to have problems.

Chris.

[sharps4590]

I wasn't debating anything. The question of hot or mild primers for BP goes back almost to the introduction of the percussion system of ignition by the good Rev. Alexander Forsyth in about 1804. If no definitive answer has been agreed on in 118 years, I doubt it will be. All I was saying is what I use. That's how the stick floated when I started shooting BPCR's 40 some years ago. That and original firearms from the BP era do have quite large firing pins and subsequent firing pin holes than smokeless firearms. And often German firearms are even larger because some Berdan primers are quite a bit bigger than Boxer, large pistol primers. I would think that with softer pistol primers an occasional primer flowing back into that probably enlarged firing pin hole a thing to just about be expected. Were it mine, I wouldn't be surprised nor would I worry about it.

[MaLar]

My guess is bolt face firing pin hole compared to firing pin diameter.