CCI Large Pistol Primers in 45-70 (Trapdoor pressures)

[sleepysquirrel2]

Does anyone do this?

I'm less worried about pressure levels, since these loads will be trapdoor pressures (~20,000 CUP) which is far less that 44 mag pressures which work fine with LPP.
I've also heard stories of people intentionally using pistol primers for a easier ignition when loading 45-70 black powder.

But will the difference in primer height cause a problem in terms of primer setback and pierced primers, especially with a strong firing pin like a trapdoor springfield?



I ran out of large rifle primers, and i'm not in the mood to pay the scalpers on gunbroker $0.25 per primer...

 

[FROGO207]

Before loading up any rounds you might prime a few cases and see if the firing pin will set them off. It may be OK depending on the length of the firing pin. The low pressure loads should work without problems if you can get them to ignite first.

 

[sleepysquirrel2]

Alright, so reaching the primers is not a problem.

Here are four cases loaded with the primers visibly below flush



As I suspected, primer setback might be an issue. You can see one of the primers here is dark, showing that it was pierced, if even slightly, venting the primer gases into the breech.



I'm not sure if it's an issue of the firing pin being too sharp, or the primer having too much room to move back, so that it stretches and tears across the firing pin due to the excessive primer "head space".

Unfortunately I'm completely out of large rifle primers, other wise i would be able to test a couple of the LRP and see if it has the same effect



Now I know others on this forum have used large pistol primers in their 45-70 loads before, the question is was it for modern rifles, or for something like the trapdoor with it's heavy firing pin and hammer spring?

Here's just an example of other folks who report using LPP in their 45-70's. I would love to hear people with personal experience doing this, and what kind of rifles they've successfully used it in, especially if it's a trapdoor. Because maybe i just need to stone the firing pin on mine to shorten it a couple thou and smooth it out, and that would solve the problem.

https://www.thehighroad.org/index.php?threads/sharps-45-70-bp-loading.886518/#post-11884176
https://www.thehighroad.org/index.php?threads/45-70-black-powder-reloading.863092/#post-11381428
https://www.thehighroad.org/index.php?threads/bp-load-in-a-45-70.233150/#post-2839887
https://www.thehighroad.org/index.php?threads/cast-my-first-45-70s.739275/#post-9275478

 

[CoalCrackerAl]

I use large pistol primers all the time for rifle loads with cast data. It works out good.

 

[sleepysquirrel2]

I use large pistol primers all the time for rifle loads with cast data. It works out good.

Any issues with primer setback or piercing? Or do they look indistinguishable from using normal Large Rifle primers

 

[CoalCrackerAl]

No signs from piercing and no set back. I use them in 7.62x54 R,30.06,30/30 ,7.62x39 and 7.65x53. Mostly with the dot powders and unique. Data from lymans 3rd and 4th cast. Oh i did have piercing with my Mosin Nagant. I had to adjust the firing pin. The adjustment solved the issue. I would feel a light puff of air when it occurred.

 

[sleepysquirrel2]

Oh i did have piercing with my Mosin Nagant. I had to adjust the firing pin. The adjustment solved the issue. I would feel a light puff of air when it occurred.

Ah that's what I fear is happening with mine (see the picture with one showing a pierced primer). How do you mean you "adjusted" the firing pin?
Shortened it slightly with a fine india stone?
And did it still work with proper LRP ammo afterwards?

Thankfully trapdoor firing pins are only $20-$30 and readily available, so if I shorten it too far it won't be the end of the world

 

[CoalCrackerAl]

No stone. The rifle works fine with large rifle. You tube how to adjust the pin on your rifle.

 

[EricBu]

Does anyone do this?

I'm less worried about pressure levels, since these loads will be trapdoor pressures (~20,000 CUP) which is far less that 44 mag pressures which work fine with LPP.
I've also heard stories of people intentionally using pistol primers for a easier ignition when loading 45-70 black powder.

But will the difference in primer height cause a problem in terms of primer setback and pierced primers, especially with a strong firing pin like a trapdoor springfield?

View attachment 1101720

I ran out of large rifle primers, and i'm not in the mood to pay the scalpers on gunbroker $0.25 per primer...

Do you have Large Pistol Magnum? They might hold up a bit better under that heavy trapdoor hammer.

 

[bluetopper]

I use large pistol primers in my CVA single shot 444 Marlin with max loadings. No ill effects whatsoever.