Kind of a weird thing......Or, "Conundrum of the Day"

[Mikej]

I had a live round I picked up at the range, and brought home. A fine, new looking piece of .357 mag. I'd pulled the bullet because it was Starline brass and figured it was a reload. Just playing, weighed the powder and figured it to be a proper load of 2400. there it's sat, on the bench. Forward to yesterday. I had a factory round out of a box of .357 mag that split when I shot it in my M94. I figured I'd pop the primer, from that found round, in my M66 and that would fill out the 50 box to process. After popping that primer, out the back door, (LOUDER than I though it would be!), the cylinder wouldn't open!? Easily. Turned out that primer bulged, or backed out, just enough to hold up the cylinder from swinging out freely.

I got my hand primer out and tried to re-seat the primer. I don't think it had backed out because it felt plenty tight and I'm not sure it moved. The I put a sizing/de-cap die in the press and pressed a couple other primers first to feel, and then pressed that funky primer out. Didn't notice any difference. Anybody got an idea why that primer did this?

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[RVTECH]

Small or restricted primer flash hole causing blowback.

Maybe loaded with a SR Magnum primer.

Possibly a dirty (or shallow) primer pocket and it seated deep enough to clear the frame and then expanded slightly, but just enough to drag on the frame.

 

[Member 5605]

Possibly a dirty (or shallow) primer pocket and it seated deep enough to clear the frame and then expanded slightly, but just enough to drag on the frame.

This I've had happen a few times.

 

[Mikej]

This is why I noted a "fine looking" round. Who ever loaded it seemed to take some pride in his work. Not that a plugged flash hole couldn't get past "US". Though after I pulled the bullet and emptied the powder I don't think I looked at the flash hole.

Do you really think a small rifle magnum would carry that much POP?

Small or restricted primer flash hole causing blowback.

Maybe loaded with a SR Magnum primer.

Possibly a dirty (or shallow) primer pocket and it seated deep enough to clear the frame and then expanded slightly, but just enough to drag on the frame.

This I've had happen a few times.

Well it sure wasn't much.

 

[RVTECH]

This I've had happen a few times.

Seems I have as well but it's been a while.

I want to say it was with S & B brass which have very tight primer pockets and some of my primers may have not seated all the way and may have been just enough to clear on loading but expanded slightly on firing.

 

[edzz]

Very normal.
When a round is fired and the primer ignites, the gas from the primer presses the primer backwards away from the case where upon it is stopped by the breach face. As this is happening the gasses are also passing thru the flash hole and igniting the powder charge. When the powder charge ignites the first thing to happen is for the cartridge case to move rearward "reseating" the primer. Than the gasses from the powder charge expand the case in the chamber and force the bullet out the barrel.

Poorly worded explication , hope it makes sense.

Back in the day (when primers were available / affordable) we often would press cases into a thin (~1/2 inch) sheet of paraffin and use these loads for short range indoor practice. We would notch the rims for easy identification and open the flash hole significantly to prevent the the primer from setting back and causing the drag you noticed.

 

[umrek]

I think edzz is correct. Without a proper charge the case isn't moving rearward keeping up with the primer movement.

I had these plastic practice bullets in the past, Xbullet or something, that you loaded into an empty case with just a primer. No powder. The manufacturer recommended enlarging the flash hole with a drill bit. My guess is that it was to mitigate what you experienced.

 

[P7M13]

It felt like it. Humming a tune, it thought, "I think I'll do some government work today...."

 

[Mikej]

Very normal.
When a round is fired and the primer ignites, the gas from the primer presses the primer backwards away from the case where upon it is stopped by the breach face. As this is happening the gasses are also passing thru the flash hole and igniting the powder charge. When the powder charge ignites the first thing to happen is for the cartridge case to move rearward "reseating" the primer. Than the gasses from the powder charge expand the case in the chamber and force the bullet out the barrel.

Poorly worded explication , hope it makes sense.

Back in the day (when primers were available / affordable) we often would press cases into a thin (~1/2 inch) sheet of paraffin and use these loads for short range indoor practice. We would notch the rims for easy identification and open the flash hole significantly to prevent the the primer from setting back and causing the drag you noticed.

That actually makes perfect sense to me. I never would have thought the gasses from primer popping would be that much more than the flash hole could handle. I'd only fired a primer in a rifle once in the garage before. I wasn't loud at all. Doing the same thing in a 4" barreled revolver was quite loud. So much so you could scar the poop out of someone, if you had the desire, loading up your revolver with only primed brass and firing at someone, say, messing with your car?

 

[Certaindeaf]

That actually makes perfect sense to me. I never would have thought the gasses from primer popping would be that much more than the flash hole could handle. I'd only fired a primer in a rifle once in the garage before. I wasn't loud at all. Doing the same thing in a 4" barreled revolver was quite loud. So much so you could scar the poop out of someone, if you had the desire, loading up your revolver with only primed brass and firing at someone, say, messing with your car?

A compressed charge of Blue Dot topped with a lead semi wadcutter is better.

 

[Stomper]

It felt like it. Humming a tune, it thought, "I think I'll do some government work today...."

THE END!