Converting an inline muzzleloader to a cartridge

DrSpeed

Four Pointer
Has anyone seen or heard anything about doing this? I know everyone and their brother has done it for cap and ball revolvers. I'm thinking BP cartridges only obviously, but I'm wondering if one could ream out a breech plug for .50-70 or a barrel liner (with O-rings for alignment and to save the rifling) for .32-20/.25-20/.32/38/45 bp loads.

My traditions sits in the safe for all but 2 weeks a year, so I figured I would see if I could change that. Beats trying to find a NEF or H&R with multiple barrels these days, that's for sure.
 

surveyor

Twelve Pointer
The first issue I see is that the rearward pressure of a muzzleloader charge is on the breech plug which is transferred to the barrel via threading.

A cartridge load would bear on the face of the action, and whatever locking mechanism is in place would need to be able to withstand any pressure that may put it out of battery.

Pressures will be low normally, so that helps, and I'm not familiar with the Traditions set up, so that's just my off hand impression.
 

DrSpeed

Four Pointer
The first issue I see is that the rearward pressure of a muzzleloader charge is on the breech plug which is transferred to the barrel via threading.

A cartridge load would bear on the face of the action, and whatever locking mechanism is in place would need to be able to withstand any pressure that may put it out of battery.

Pressures will be low normally, so that helps, and I'm not familiar with the Traditions set up, so that's just my off hand impression.
Your impression is right, and the technical "out of battery" condition would be my only real concern.

It's really a standard break action, but I don't know what steel they us for their receiver. I know H&R's cast iron SB1 receivers are good for shotgun, 357,44, 22hornet, and .30-30. That lends me some confidence that it can handle black power cartridges if it's made out of literally any gun-worthy steel.
 

surveyor

Twelve Pointer
I've massaged a fair number of single shots and SXS into something different, and your reference to 30-30 reminds me of my only negative experience.

The action I used wasn't set up to handle a blown rifle primer.

It vented through the action and split the grip. I avoided serious injury but it did alert me to that mechanism of oops as well.
 

surveyor

Twelve Pointer
And I'm not discouraging the goal here. In fact, I'm all in, because we're human; just making sure all the bases are at least touched, if not stepped on hard.
 

DrSpeed

Four Pointer
I've massaged a fair number of single shots and SXS into something different, and your reference to 30-30 reminds me of my only negative experience.

The action I used wasn't set up to handle a blown rifle primer.

It vented through the action and split the grip. I avoided serious injury but it did alert me to that mechanism of oops as well.
I'm glad you lived through it relatively unscathed, it's experiences like that that keep me from pushing it that far anyway. I only mentioned .30-30 because it's what I saw in some of the forums on the SB1, none of NEF's recent official literature endorse anything other than shotgun and revolver calibers.

But back to the matter at hand, I see how there could be a bigger issue with how the action is designed. Do you recall what caused your primer failure?
I would be curious of the risk with factory bp or cowboy action loads in .38 or smaller, I imagine it's still there, but is hopefully a scale of magnitude smaller or easier to contain.
 

surveyor

Twelve Pointer
I'm glad you lived through it relatively unscathed, it's experiences like that that keep me from pushing it that far anyway. I only mentioned .30-30 because it's what I saw in some of the forums on the SB1, none of NEF's recent official literature endorse anything other than shotgun and revolver calibers.

But back to the matter at hand, I see how there could be a bigger issue with how the action is designed. Do you recall what caused your primer failure?
I would be curious of the risk with factory bp or cowboy action loads in .38 or smaller, I imagine it's still there, but is hopefully a scale of magnitude smaller or easier to contain.
I could not duplicate the situation a second time.

Could have been a faulty primer but as much as I hate to admit it, the probable cause would be loose nut on the reloading bench.

As a result, I reprocessed my reloading techniques.

And studied hard on bushing firing pins, and gas vent channels as well.
 

45/70 hunter

Twelve Pointer
You could just pick up a single shot shotgun and get pistol caliber barrel liner. I've seen them up to 18" long.
 

DrSpeed

Four Pointer
You could just pick up a single shot shotgun and get pistol caliber barrel liner. I've seen them up to 18" long.
I have thought about this, in addition to reeming out the breech plug to .410 chamber and using .410 adapters. The only issue is the only place I can find that makes rifle length ones is chaszel. They seem to be perpetually out of stock as a small batch machine shop.

I do have the son's .410 single shot, but it's not drilled and tapped 😄
Track of the wolf sells by the inch and has all those nifty BP calibers available.
I saw that too, but the only barrel liners that would go down a .50 cal, with room for O-rings, would be .32-20 and .25-20. I would really dig a .38 or 45, but the liner is too thick
 
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DrSpeed

Four Pointer
After doing some more research, I might buy a "armslist special" muzzleloader to test this out.

.50-70 reads to be a strangely practical conversion, but I don't really have the guts to shoot it, except out of a vice with 30ft string 🤣. I wish I could find a pistol cartridge equivalent, like a .50 Scofield or long colt, but nothing like that exists.
 

surveyor

Twelve Pointer
I saw that too, but the only barrel liners that would go down a .50 cal, with room for O-rings, would be .32-20 and .25-20. I would really dig a .38 or 45, but the liner is too thick
Somewhere, I wrote a spreadsheet for hoop stress, and given the liner material, typical pressures, and a safety factor, see how much meat you need for the liner thickness, but yeah, sleeving a 50 cal will be hard for a 38 nominal, and dern near a hard nope for 45.
 

DrSpeed

Four Pointer
Somewhere, I wrote a spreadsheet for hoop stress, and given the liner material, typical pressures, and a safety factor, see how much meat you need for the liner thickness, but yeah, sleeving a 50 cal will be hard for a 38 nominal, and dern near a hard nope for 45.
I figured that might be the case for .45, which is unfornate. One of the short .45 bp cartridges would be ideal performance wise.

Funny thing is that machine shop has managed a .38 adapter for a .410 shotgun, or at least advertised it. No idea how they worked it out though.
 

surveyor

Twelve Pointer
I figured that might be the case for .45, which is unfornate. One of the short .45 bp cartridges would be ideal performance wise.

Funny thing is that machine shop has managed a .38 adapter for a .410 shotgun, or at least advertised it. No idea how they worked it out though.
Maybe a chamber adapter only, and it just just freeballs down the barrel?
 

surveyor

Twelve Pointer
Ok, now I'm piqued.

Groove diameter of .357,

O.D to fit in barrel must be 0.410

leaves 0.053 or a thickness of 0.026, correct?

Hmmmm. Got to run those numbers. Obviously it works, just wondering what you could maximize into a 50 cal, size and pressure wise.
 
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surveyor

Twelve Pointer
Just got to work and looking for my hoop stress calculator, but I have a couple thoughts.

Pressure for cartridge rounds is higher in the chamber and goes down dramatically after that, so the adapter probably maximizes the 410 chamber and thins out for the rest of the liner.

That said, What is the OD of the threads for the breech plug in your Traditions?

It would take machine work, but if you get a sleeve that comes in the larger diameter like TOTW's, turn it down to sub nominal 50 cal for the barrel portion - so it doesn't contact the threads, thread the OD of the chamber area to match the OD of your breech plug, leave a recess at the muzzle end for an O-Ring for centering, you could be in business. Just slide it in, screw it tight, and seat the muzzle O ring.

The only thing to work on would be an extractor unless you wanted to ram rod them out. You could always leave a little rim relief slot and have something like a decapper.

I am reminded of an Allen Drop Breech gun, originally chambered in 44 Rimfire that I realigned the firing pin, and rechambered in 44 Special (BP only). I chose that so it wouldn't accidentally chamber a 44 magnum.

That was a fun shooting gun. Duplicated a 44-40 ballistically. In fact, I shot 44-40 cast bullets from it.

That wouldn't be up to 45 colt, but it would be a hoot to shoot.

(edit to add: You can kill a deer with a 44 BP Special ;) )

I still have the 44 chamber reamer.
 
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DrSpeed

Four Pointer
Just got to work and looking for my hoop stress calculator, but I have a couple thoughts.

Pressure for cartridge rounds is higher in the chamber and goes down dramatically after that, so the adapter probably maximizes the 410 chamber and thins out for the rest of the liner.

That said, What is the OD of the threads for the breech plug in your Traditions?

It would take machine work, but if you get a sleeve that comes in the larger diameter like TOTW's, turn it down to sub nominal 50 cal for the barrel portion - so it doesn't contact the threads, thread the OD of the chamber area to match the OD of your breech plug, leave a recess at the muzzle end for an O-Ring for centering, you could be in business. Just slide it in, screw it tight, and seat the muzzle O ring.

The only thing to work on would be an extractor unless you wanted to ram rod them out. You could always leave a little rim relief slot and have something like a decapper.

I am reminded of an Allen Drop Breech gun, originally chambered in 44 Rimfire that I realigned the firing pin, and rechambered in 44 Special (BP only). I chose that so it wouldn't accidentally chamber a 44 magnum.

That was a fun shooting gun. Duplicated a 44-40 ballistically. In fact, I shot 44-40 cast bullets from it.

That wouldn't be up to 45 colt, but it would be a hoot to shoot.

(edit to add: You can kill a deer with a 44 BP Special ;) )

I still have the 44 chamber reamer.
If I recall correctly, the OD of the threads is .625, the plug is 5/8x18.

what you're describing is pretty close to to what I was thinking of doing. My reasoning for looking for the sub .50 liners was to avoid the excess machining. I was hoping to thread or press-fit the chamber end into a spare reamed out breech plug.

What your saying sounds like the more feasible way to go, given my options for liners.

I still might find a disposable break action to try it before my hunting rig.

But....other than ammo, reaming the plug out for .50-70 would by far the easiest 😁.
 
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Mr.Gadget

Old Mossy Horns
I have a BP gun done that way.
Called a 1866 second Allin 50-70.
Started as a 1861 Springfield. Fun to shoot.

There are several others I know done in different pistol rounds.
It is all about the loading. Keep it BP and light loads. None I know of use a threaded in section or barrel.

Also have some Standard Trapdoor 45-70 that were lined. Liner is very thin. Shoot great.
 

pattersonj11

Old Mossy Horns
Ok, now I'm piqued.

Groove diameter of .357,

O.D to fit in barrel must be 0.410

leaves 0.053 or a thickness of 0.026, correct?

Hmmmm. Got to run those numbers. Obviously it works, just wondering what you could maximize into a 50 cal, size and pressure wise.

.410 pressure and .38 special are pretty similar. Just need something to fill the gap. The chamber and barrel should hold the pressure easily.....especially with the added thickness. It would have to be a snug fit to keep from deforming.

.357 mag or max would be a different beast....but it probably would go. They could go up a thousandth or so on the rifling diameter to alleviate a little pressure.
 
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