Build ml shotgun from modern barrels

[In Over My Head]

Was visiting a friend today and he had acquired a ton of gun junk. He had a barrel full of orphaned SxS cartridge shotgun barrels and several standing breeches (?) with tangs, which had openings to accept hooked breeches.

What are the pros and cons of using a cartridge barrel to build a muzzleloading shotgun? Is it doable in any practical sense?

I'm thinking I'd want to select particularly thick barrels so I could cut off most of the chamber end and still have enough meat for breech threads. Also preferring cylinder bore or thicker barrels that could withstand having the choke bored out of them?

Should I just get this out of my head before I start or should I start looking through those barrels?

 

[In Over My Head]

Found this thread, still searching,,,
http://www.muzzleloadingforum.com/fusionbb/showtopic.php?tid/290488/

 

[ohio ramrod]

Since modern barrels are made to withstand far greater pressures than black powder produces it is perfectly safe as long as you fit the breech plugs properly and allow enough steel under any dovetail grooves you cut. :idunno:

 

[DickS]

In the thread you found, Brockway's book is mentioned. Getting a copy would answer a lot of questions for you.

 

[In Over My Head]

Yes, apparently getting Brockway's book is essential to this quest. I will acquire it.

But I was hoping to hear some comments along the line of: "Yes, this is readily doable, watch out for this, this and this." or "Don't waste your time, this is a fool's errand."

I guess if the topic is worth writing a book about it must not be a fool's errand!

 

[19 16 6]

I looked at doing a flintlock double gun build here in Aust. My best options given to me by gunsmiths was to use a second hand barrel set off of a break action modern shotgun.
This was mainly because of cost & availability.
Many things are different here than in the U.S.A & we do not have ready access to new parts options like you do.

Personally what I would be looking for in a barrel set would be wall thickness both at the chamber & at the choke. The chambers need cutting off & then the wall thickness needs to be plenty thick enough to be threaded safely for a breech plug. The chokes on a thick barrel have plenty meat there to be reamed to whatever you desire. Ample length like 32" should give you a set of barrels finished around the 28" mark
From your OP I think you already know all that.
I would not be scared of using a good set of Damascus or twist barrels if they were thick enough. If they are a bit rough inside check to see if they can safely be back bored to clean them up. This type barrel set will look good but have soft soldered ribs that may need to be re layed ( removed, cleaned & re soldered) if no longer sound.
Cheaper makes of guns in more modern times have a barrel set that has brazed top & bottom ribs. these things are tough & sound & can take a darn good hot blueing but the soft solder ribs cannot. It should also be easier to solder or drill & tap the ramrod thimbles & any lugs for wedges to a brazed bottom rib with out disturbing it.
O.

My optimum choice would be long & heavy wall with brazed ribs.

 

[Zonie]

For your first tidbit of information about chambering the barrels:

The chamber in a modern 12 guage is tapered, being larger at the rear than the front.

The chamber diameter at the rear is .812" in diameter.
2 3/4" or 3" forward from this, the chamber diameter reduces to a diameter of .798".

Although most muzzleloading rifle barrels I's aware of shoulder the front of their breech plugs against a shoulder where the thread ends, IMO, a big smoothbore breech plug doesn't absolutely have to seal against a shoulder in this area.

The breechplug can be made to mate against the rear end of the barrel to provide a gas tight seal.

With this in mind and knowing the size of the existing chamber, I checked out the thread dimensions for a 7/8-14UNF-2B internal thread.

It turns out, the minor (small) diameter of this thread is .798-.814".

This makes the existing chamber, exactly the right size for a 7/8-14UNF-2B thread so, it seems, the existing 12 guage barrels are already machined for your new breech plug.

All you have to do is to cut the rear of the barrel off so you have at least 3/4 inches of chamber left and thread the remaining chamber.

Of course, the area of the cut will have to be filed to be totally flat and perpinduclar to the axis of the thread to make the sealing surface for the breech plug. :thumbsup:

 

[Supercracker]

I tried this a while back. In 3 different sets of twist breech loader barrels not a single chamber was perfectly in line with the bore and cone. I think it must have something to do with the way they were making the barrels at that time. This made getting a plug to match up with the bore and seal on the forcing cone a colossal PITA. If you had to use a set of breech loader barrels I think the only way to really do it perfectly would be to get a chamber reamer and and ream the chamber and cone on a lathe to that known profile and in line with each other then you can machine a plug to that known profile.

By the time you get a good barrel set, get a reamer and do this work, you could have gotten a nice set of shootable percussion barrels and just made breech plugs for them. I decided this was a more reasonable option. Doubly so when you consider that will also save you from having to make and solder on RR tubes and if you're careful finding a donor gun you can reuse the original Buttplate, Triggers and triggerguard on your flinter.

my .02

 

[Zonie]

I think if you re-read my comments you will notice that I did not suggest trying to seal the breech plug on the forcing cone.

I suggested making a shoulder larger than the breech plug threads which would seal against the rear of the barrel.

 

[Supercracker]

I think if you re-read my comments you will notice that I did not suggest trying to seal the breech plug on the forcing cone.

I suggested making a shoulder larger than the breech plug threads which would seal against the rear of the barrel.

Sorry, I didn't think you had. Mating to the forcing cone as well as the breech face is what Brockways book suggests. I agree, if you had a good seal at the face it's probably not terribly important. I think any small gaps at the threads of cone would almost immediately fill up with fouling and then when that gets saturated with oil after the first cleaning it will all be good. I'm just picky about those kinds of things, perhaps to a slight OCD level. The chance for gaps where powder could theoretically accumulate scares me. OTOH, It could probably be no more than a grain or so which would be unlikely to cause damage, but it can still cause corrosion, but that will be mitigated by oil saturation..............and now were back to the never ending OCD conversation in my head. lol

 

[In Over My Head]

Thanks for the continuing discussion!

Brockway's book is on it's way.

He's got so many barrels to choose from that I'm pretty hopeful of finding a pair that will lend itself to this.

He's saying he's got locks to choose from, too. But I'm guessing any external hammer locks he has are from cartridge guns. Are these adaptable to my needs? It seems like they would adapt since they are basically an early evolution from percussion locks, but I have a feeling I'll be borrowing trouble with his old locks.

I see a couple of choices of new-made matching left and right locks, but only percussion. I'm probably already thinking way beyond my skill level, but how would I move this project towards flint locks?

 

[DickS]

Matching pairs of flintlocks are available. Look up L&R or Track of the Wolf.
Cartridge gun locks will most likely have rebounding hammers. Not suitable for ML percussion use. If a pair of locks do have half and full cock notches, they might be adaptable, with new hammers, maybe lockplates.

 

[In Over My Head]

Wow! What have I gotten myself into?

Since I last posted I've received Brockway's book and read it through. What a reference! He leaves no stone unturned.

If... I can complete this project, it will be a lifetime accomplishment. The fully atrophied right side of my brain is trembling in fear and anticipation.

It occurs to me that this is every bit of a ten year project - at least. I am highly unprepared and preliminaries - like wiring and lighting my shop, learning to use my lathe, etc. will probably take two years. But this will give reason to my existence in retirement!

Today I went through my buddies pile of orphan barrels. I chose a set of Liege-proofed 16 gauge Damascus or twist barrels. (If there's a difference, I guess they're twist.) If I'm reading the proof marks correctly they've passed "optional superior provisional proof". Whatever that means, I think they were a fine pair of barrels in their day.

Here's where I get to my latest question. The barrels are thoroughly surface rusted. Not heavily rusted, not pitted, you can still plainly see the twist pattern but they are thoroughly surface rusted. (The bores shine and have no notable pitting although they are a little rough near the muzzles from they way they were stored.)

How can I neutralize this rust so there is no further rusting or damage while these barrels continue in storage until I can really dive into the project?

I was thinking of soaking them in vinegar but I'm leery because of them being twist construction.

Suggestions?

TIA

By the way, I know I'm cliff-diving into deep water choosing this as my first build attempt. Indeed I may start and complete something else in the interim. I found a post by Mike Brooks where he said you couldn't force him to ever build another SxS flintlock shotgun. So I'm laying the mental groundwork to approach this with a great deal of patience. I know it will have to be a very long project if there's any hope of doing justice to the parts.

 

[19 16 6]

Those barrels sound alright to me. Measure the bore size, it should be .662" or near to. This is just to make sure that the shiny bores are not a result of excessive honing out of rust pits.
They may not sound so good to a lot of people because they are scared by all the bad said about Damascus & Twist barrels.
I urge you to do an in depth search on the safety of Damascus barrels & read about the tests done with high pressure smokeless loads.
You will see that it took pressures in excess of 20,000 psi to start a bulge & a lot higher to rupture them. Black powder is low pressure & sensible loads in a 16 gauge will top out somewhere in the 6,000 psi range.
So before being freaked out educate yourself.
O.

 

[19 16 6]

How can I neutralize this rust so there is no further rusting or damage while these barrels continue in storage until I can really dive into the project?

Suggestions?

What about oil ?
O.

 

[In Over My Head]

Why do I think oiling rust does not kill the rust? I thought the general scheme of things was to remove the rust and oil the metal.

 

[gunmaker43]

Naval jelly and steel wool. Longer it's on metal, better it works.....

 

[19 16 6]

You stated that you want to stop further rusting on the barrels till you can get to the job.
Oil should do that.
Blue, black & brown gun finishes are all a controlled rusting process that gives us a porous surface to hold oil against the steel to prevent further rust breakout.
Now if'n you had stated, "How do I get this rust off", I mighta said different. :v
O.

 

[nwtradegun]

once you have left it on long enough pour boiling water over it. it stops rust. dry and oil it down.

 

[In Over My Head]

I'm hearing the advice - but I'm still a little leery of putting Naval Jelly on twist steel.

I guess I'd like to see more replies before I do that.

No offense.