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Practically Shooting

Had a Primer Explosion Last Night

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I had my first primer explosion last night. "Explosion" is the wrong word I'm sure. It went bang outside of a firearm.

I started reloading in 1981 or 82, and that was my first. I have seen so many primers mangled from reloading mistakes and malfunctions I had begun to wonder if they were as sensitive as made out.

Well, they are if you catch them right.

I was priming .223 cases. Tool was a Lee Auto-Prime with primer feed tray. Primers were Federal number 100 Small Rifle. Not that it matters, if the cause is what the evidence leads me to believe.

I had barely started to squeeze the handle to seat one- just the slightest pressure- and POP!

It was pretty loud in the garage.

The clear plastic top cover of the primer tray disappeared. The remaining 30-ish primers went with it. I found two small pieces of the cover later, but the rest is still missing.

I had some black scorch marks on both thumbs. The left thumb stung for a while. I later found a tiny sliver of metal in my right thumb- probably part of a primer cup.

Cause analysis:

I removed the shellholder and case. A primer anvil slid out from on top of the priming punch. It was oriented point-up.

My best guess is that anvil came loose from a primer when I put them in the tray. It worked its way onto the seating punch and became a firing pin.

With each case I will be watching the punch for foreign material more closely than before. I want to remind or suggest the same for all.

The anvil was charcoal gray-black, down in a black plastic opening with little light entering, so a light may be a good idea.

I went back later to prime more, but quit after about ten. I was a bit nervous about it.

Just letting everyone know: It does happen.

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Reposted from a couple years ago:

I have asked friends who have reloaded for many years and not one of them have had a primer go off while reloading.

Personally, I have experimented to see how hard/easy they could be set off. I found that if you directly dent the primer, like a firing pin would, that you can get them to go off. However, you have to hit them darn hard and make a significant dent. I have thrown them on the floor as hard as I could and slowly crushed them in a vise, just can't get them to go off this way.

My experimentation stopped when I finally got one to explode. I had no idea how much force they have or how loud they are. I did have leather gloves and safety glasses on, but the force through the leather glove left my finger bleeding and my ears rang for a while. Folks, DO NOT experiment with primers, take it from someone who had to learn the hard way.


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The noise was amazing. I have fired empty primed cases in guns before, and shot primer powered ammo, but had never heard one go off practically in the open like that. My left ear was closest to it, and it hurt at first then rang for a while.

I still have not found the plastic top cover for the primer tray.

After looking it over from a new perspective, I really don't like the Lee Auto-Primes design. The primer being seated has a line of primers right up against it. Nothing separates the primer being seated from the other dozens in the tray.

To their credit, I heard yesterday the newer Lee tool has a way to block this off.

I have an RCBS tool also (broke when dropped) and it's handle moves a "gate" that slides across and blocks those in the tray.

Many people have expressed concerns over progressive machines having a tube full of primers. The only one I've used is Dillon, and they work by plucking the bottom primer from the tube, carrying it to the shellholder, then seating it. So while there is a tube full of primers, the actual seating operation is done apart from it.

After posting this incident elsewhere, several people responded with something along the lines of "Of course you don't use Federal primers in a Lee Auto-Prime, it says so right in the instructions".

Huh? It does?

I checked, and the instructions from my original (1982/83) tool says nothing about it. A-ha!

Then I checked the instructions for the one I bought a couple of years ago (to leave one setup for small primers and one for large) and there it was. After a big bold WARNING, it says not to use Federal primers in it.

Guess which one I had never read the instructions to? "I've been using these for 30 years, I don't need no stinking instructions!"

However, the wording is odd, and comes after talking about different primers having different force when they are fired. Nothing about their sensitivity. It almost makes it sound as if they are forbidden because they are too weak or too strong and accuracy or reliability will suffer.

Still, I must admit it says not to use them, and I did.

I think with the anvil sitting on the seating punch as it was, any brand would have fired. Maybe even Wolf.

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I have always wondered about a primer going off while using a hand primer.

I have a Hornady hand primer and it has no separation between the primer being seated and the others except that the primer is moved away (maybe 3/8") from the others when it is pushed by the ram up to the case.

I now use the primer tube that fits onto my press. It does as you described; plucks a primer from the tube then presses it into the case completely separated from the others.

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  • 2 weeks later...

I usually use an RCBS bench-mounted priming tool which does separate the individual primer being seated, from the tube. I must admit, though, that I do get nervous sometimes with all those primers in that skinny little tube- primers are NO toy, that is for sure.

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