What's all about pierced primers in O/U?

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calvados.boulard

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Hi everyone,

So I have read about pierced primers in O/Us wearing down firing pins on numerous forums. There is also much mention of other damage that piercing primers can do do an O/U, but nothing much more specific than that. Some mention that your internals (trigger etc) can get dirty. So can someone tell me, asides from wearing down your firing pins (which are a fairly easy and cheap item to replace), what other damage can piercing primers cause to an otherwise quality O/U?

Thanks,
Cal.
 
A pierced primer will vent hot gas, albeit in small quantity, toward the firing pin. Because there is a small amount of air-gap around the pin into the action and trigger mechanism, the gas will continue in this direction, carrying with it a small amount of carbon and debris from the burnt powder.

Once or twice, this isn't a concern. Over time, the debris will build up inside the workings of the gun and act like grit on the moving parts, wearing them down.
 
For me the issue was only with Cheddite primers in the bottom barrel. It was a very mild pierce- if you looked at the primer you would just see a little black dot. Eventually this ate a small crater in the end of the firing pin. I stopped using cheddite primers and shoot almost 100% federal primers now and haven't had a pierced one since. I don't think the other posters are talking about the type of piercing you are talking about OP...
 
cartwheel said:
For me the issue was only with Cheddite primers in the bottom barrel. It was a very mild pierce- if you looked at the primer you would just see a little black dot. Eventually this ate a small crater in the end of the firing pin. I stopped using cheddite primers and shoot almost 100% federal primers now and haven't had a pierced one since. I don't think the other posters are talking about the type of piercing you are talking about OP...
Click to expand...

I concur. (Talking reloads here)...Most always it's a cheddite issue, it erodes the tip/nose of the firing pin. W209's for me.
 
Had a new Win. 101 piercing primers on the bottom barrel one time. The bottom pin was a tad long with a sharper point. Had a gunsmith round it off a bit and no more issues. So if you are piercing primers take a look at the pin fore being to long or misshapen.
 
It is indeed Cheddite primers in factory challenger loads that is the source of the pierced primers. They aren't massively blown open or anything, but there is a trace of black carbon on the primer after firing. Only bottom barrel does this with any regularity. Top barrel it only happens rarely. Shooting anything but challenger and there's no carbon or piercing to be found.

Thanks,
Cal.
 
Some guns are prone to this, some primers are more prone to allowing it to happen(Cheddite & Remington). I am currently using Cheddite primers in all my reloads, none of my guns seem to have issues with them. From what I seen round the club, Browning, Kreighoff and Kolar seem to be the worst offenders for lower barrel primer piercing. Coincidentally, Kreighoffs and Remington Gun Clubs seem to also be a bad combination. What happens when the primer gets pierced, is the crap from the load gets in the action and burns the tip on the firing pin and over time will ruin the pin.
 
mrgoat said:
Had a new Win. 101 piercing primers on the bottom barrel one time. The bottom pin was a tad long with a sharper point. Had a gunsmith round it off a bit and no more issues. So if you are piercing primers take a look at the pin fore being to long or misshapen.
Click to expand...

I think my above pin issue was very isolated. Just a bad pin that went unnoticed during assembly. I always used CCI or Win 209's in AA hulls at the time this occurred. Never had it happen again with any shotgun or cartridge combination.
 
I've had primers pierced on the lower barrel on one of my O/U's - particularly when shooting Challenger loads, which I believe are Cheddite primed. The lower barrel on most O/U's have a firing pin that is not on the same axis as the bore - its off by about 30 degrees. In my case, I re-radiussed the firing pin to match the offset angle - problem solved.
 
Had to take a couple thousandths off the firing pins of a CZ Bobwhite... the firing pins were piercing the primers and sticking in them, locking the action... the gun went back for this problem twice... it's been good since.
 
calvados.boulard said:
It is indeed Cheddite primers in factory challenger loads that is the source of the pierced primers. They aren't massively blown open or anything, but there is a trace of black carbon on the primer after firing. Only bottom barrel does this with any regularity. Top barrel it only happens rarely. Shooting anything but challenger and there's no carbon or piercing to be found.

Thanks,
Cal.
Click to expand...

The problem is with the gun not the ammo.
 
Grouser said:
The problem is with the gun not the ammo.
Click to expand...

No it is not in many cases. It is a documented issue with certain production runs of cheddite 209 primers they say (imo all of them) and there was even a time where browning didnot recommend them in their shotguns
If anything IMO more due to most European primers having steel cups vs brass and the anvil in the Cheddites is closer to the striking surface than in North American primers. Cheddites use a brittle steel for their primer cups that tears rather than stretches when the pin hits it, and the fact that the Browning pin hits the primer from the above and side makes things even worse.
Yes one can cut back and reshape the firing pin to make them work but who wants to do that
Cheers
 
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I've had two shotguns do this, both Brownings. The 725 Sporting I had would occasionally pierce Cheddite primed shells in the bottom barrel only, maybe 2 out of 25. Only Cheddite, nothing else.
The firing pin stuck out about 0.062" originally, was showing signs of denting and erosion. I removed it, smoothed the surface with a stone, and reinstalled it. This happened twice, the last time I measured the pin protrusion it was at 0.052", no more problems with piercing Cheddites and the gun was 100% reliable ignition wise.
The second gun is a 20 ga. Citori Lightning, it does the same thing but much more frequently, maybe 50% of the time. In both barrels. Lucky me!
I haven't got around to measuring the pin stick out in that gun yet, and haven't tried to fix it. I'm using W209 primers in my 20 ga reloads so it's not a problem.
My ancient SKB 500 eats Cheddites like they're candy, so there is some light at the end of the tunnel. Never had a pierced primer in that gun, although the strikes are noticeably shallower than the Brownings.
 
Not much to it, I just removed the pin, looked at it through a 10x jewelers loupe, and reshaped the end with a small fine carborundum stone. I measured the overall length first to see how much was coming off, then just rounded the end to a nice smooth radius. Don't do one edge first, rather try to bring it down evenly, slowly removing the pits or eroded areas as you go.

The loupe enables you to clearly see what you're getting. You don't want flat spots, craters, or points.
Each time I did this, I rechecked the protrusion once the gun was back together so I'd know how much it was changed, and recorded those numbers. The good pin will show you the profile you should have, unless your gun has asymetrical firing pins if there is such a thing.

You could hold the pin in a cordless drill or lathe chuck to bring it down evenly. I might have used the drill once in fact, but go slow, once the material is gone there's no putting it back. Then it's new FP time, if you can get one.
I'm not a gunsmith, if you have doubts about doing this get it done professionally.
 
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