Investigation surely continues. I have been shooting everything under the sun, reloads, factory shells by Winchester, Remington, Federal, RST, Gamebore, you name it, and I have not had a problem with any shotgun, hammer, hammerless, you name it. Good luck with the search for the culprit, but 65 years of double gun shooting has not resulted in similar problems in my experience.

I used to get pierced primers pretty regularly on two of my T/A hammer 16's - one more often than the other - and almost all were on the left barrel/hammer/plunger. All were cheddites.





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firing plunger length
 

With a replaced battery, the calipers work much better. Sometimes I miss verniers. At any rate:

My plungers are .992" OAL. They stand out just over .170" from the breech face with the plungers fully depressed, if that means anything.

What length should they be/do others have? (I'll post on the hammer gun forum as well)

Thanks,
Seth

Cheddite primers are much more easily pierced than any I use in reloading their hulls. At one point I had a half dozen top lever 16s and two were notorious primer piercers. I removed them and had them ground to a very even radius as they were more sharply pointed. Never pierced another. I buy lots of Cheddite NPEs without any fears.

80% of the time, my 20 gauge top lever pierced the RST primers. The primers must be made of a thinner gauge metal. I know others have complained to RST to no avail.

Well I don't completely trust internet research, but from what I can gather they use Cheddite primers, who in turn use a little thinner gauge metal. Hammer guns, at least in some cases -including mine- seem to have pins or plungers that protrude further than others. When combined with a plunger that extends at an angle I could easily see that a thinner gauge metal would have a tendency to tear when subjected to the sideways forces from the angled impact in addition to the usual inward ones. I'm hoping to get some numbers from other members on what their plunger measurements are (without getting too personal) so that I have an idea where it would be good to end up for an overall length. The radii on both plungers are very smooth (thanks for the info, though, edgarspencer) so I'm not sure what else I could do.

Have a Remington hammer 12 that I made a new left firing pin, it pierced Cheddite primers and I shortened it 3 thou and no more problems.

Seth, it isn’t so much they use Cheddite primers, as that they use Cheddite NPEs.
I don’t know if Cheddite even sells unprimed hulls, but that would be a costly step for RST to add priming new hulls to their operation.

Sorry, I see that I was unclear-what I meant was that the thin wall of the Cheddite primers, which I would think are what's in Cheddite NPEs, seems to allow the piercing or tearing of the primer wall during firing instead of the usual deformation. But that's just the internet and my impression!

Gentlemen:
For what it's worth, I quit using Cheddite primers long ago. I switched to Federal 209s, cut my powder charge by half a grain, and have never had another problem with cup piercing or ignition.

The upshot is that I don't have to modify a classic gun to accommodate a lousy primer.