45-70 Blackpowder Gun - Looking For Info

XSlor

XSlor

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At the Chilliwack gun show, my buddy picked up an odd gun.

It's a 12gauge break action/lower with a 45-70 barrel from a black powder rifle. Basically someone took a 12 gauge like the backpacker sold by CanAm and removed the barrel and put a 45-70 barrel on it... (there was a smiths name attached to the gun, so it was "professionally" done)

So buddy buys a box of regular 45-70 ammo... I've advised him not to shoot it without having a smith look at it though. He paid around 100bucks for it... everything LOOKS good and it feels good... but I'm not sure if it would be able to handle modern day 45-70 rounds.

Anyone have any experience with these types of conversions? Also where could one find black powder 45-70 rounds?
 
Is it a single shot gun or side by side? He is probably safe sticking with black powder but it would depend on the specific action and design if it was being used to shoot modern high pressure loads. Some factory 45-70 shells are loaded for the trapdoor springfield and are relatively low pressure but I suspect that the leverution shells might be higher pressure. I have seen factory made break action single shot 45-70s but I have also heard of people adapting double barrel shotguns into double rifles using usually antique frames. I think a person needs to be knowledgeable of break action gun strengths and weakness when going that route

cheers mooncoon
 
Thank you for the feedback!

It's a single barrel gun. He actually has the same lower on another shotgun that hasn't been modified. I'll try and get the details later and post.

How does one determine the gun's "strengths and weakness"?
 
It sounds like a "barrel stubbing" job. That's where the old barrel and mount is used as a sleeve and the new barrel is machined to fit using the old barrel breech as an adapter sleeve. If done well it's a good way to go.

Shotguns are not intended for high pressure operation. And some of the .45-70 ammo out there is loaded up pretty strong. I'd have no reservations over shooting proper vintage respectful loads from the modified shotgun but I'd avoid the modern strength stuff. Basically the loads rated for being OK to shoot in the old Springfield trapdoor rifles would be fine in a barrel stubbed shotgun receiver. And it might even be OK over the long run for something slightly over the rather weak trapdoor loads. But the strong stuff intended for shooting from the Marlin and other "guide gun" lever actions or TC Encore rifles is something I'd avoid.

If you want a more technical answer it all comes down to pressure and the rate of the pressure increase slope when the round is fired. A shot shell has a given surface area for the head and achieves a given peak pressure. This produces a peak lb's/square inch pressure against the face of the receiver. The head of a .45-70 is smaller so technically you can run it at a lot higher pressure and still only put the same lb's/square inch into the face of the receiver. But I would not go that high because it may actually end up peening the face of the receiver by being over what the metal can withstand. There's also the rate at which the pressure builds. A sharp enough rise can have localized effects in the metal where a more general and slower build can be handled with ease.

I'm also going to assume that he's interested in not pushing the edge only to find that it stretches the frame over time and results in a loose lockup.

All of which suggests that the softer and more classic "trapdoor" or close to it loads are the way to go.
 
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unless stated otherwise factory ammo its loaded to trapdoor level. HSM ex. is loaded hotter and says modern action or lever action on the box(or so im told)
 
I don't buy factory ammo but my understanding is the same as what ctsmith posted. If it doesn't say anything it should be mild enough for trapdoors and for your buddy's barrel stubbed conversion.

If you get a chance piccies would be nice. I'm sure some of us have some interest in such a thing.

I'd also suggest that he's going to have sticker shock at the cost of the ammo. And a straight wall case like 45-70 is really easy to reload with a very modest equipment setup. And if he's reloading then it becomes very easy to go with black powder or one of the substitutes to reload with and get the big smoke show that can be so much fun.

There ARE some specialty ammo loaders that make BP loads in .45-70. But again they would likely be tough to find up here and expensive if he did find them. On the other hand with some powder and cast bullets he can reload his own for around 40 cents a pop for supplies. And depending on what he's finding factory ammo prices to be like the amount of ammo to pay for the gear to where he's reloading for cheap will vary.
 
If you know somebody that can load

I load 53grs. triple 7 thrown a from powder measure with a wonder wad under a 405 gr bullet for my trapdoor carbine

Mild load with smoke
 
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