using old barrels

[tnguy]

i am looking at buying a couple of old barrels that have been re breeched. one is an lc smith 28 gauge round barrel and the other is an oct to round barrel, its a 20 gauge. the lc smith barrel has had a patent breech plug installed and the oct barrel a standard breech plug. my question is with the plug seat. on the new barrels i have used the plug seats into a shoulder on the inside of the bore, well these 2 the plug threads just run out into the bore. both are tapped well and the plugs fitted nicely, but i was wondering how safe it was to re use a barrel in such a manner?
thanks

 

[paulvallandigham]

The purpose of a shoulder, is to keep gases, and residue OUT of the threads. I would avoid the barrels, unless the price was right. I would want to have the barrels shortened and a shoulder cut in the back of the bore. Frankly I am skeptical that a modern lathe would cut threads similar enough to those used in these old barrels, and plug. The threads need to match. Other opinions will vary, I am sure. :surrender: :hmm: :thumbsup:

 

[Birddog6]

My first question when I see something like that is "Why didn't they get used "? And this could be why, possibly someone didn't do it properly, or there is not enough meat in the breech to have a seat. Either way I wouldn't buy them unless they can be rebreeched properly.

Keep in mind the Barrel& Breech are the most important parts of the whole gun ! :nono: IT IS HOLDING THE CHARGE WHEN IT GOES OFF :idunno: :shocked2:
Not a good place to cut corners, IMHO. And breeching one IS a place I want someone that knows what he is doing, not "Questionable" workmanship.........

Keith Lisle

 

[Tinker2]

I am not sure why anyone would thread a barrel that way unless the
barrel was to thin. If the threads ran into the bore it would be hard to
clean.
I think I would think of the barrel the same way if the breech were pitted
as deep as the threads are cut.

If the threads in the barrel were cut/finished with a bottoming tap by a
good muzzleloading gunsmith type person, and the plug fit to that, then
all else being equal, I don’t know why it would not be ok.

I might pass on them, sight unseen.

Go with what Birddog6 said.

Tinker2

 

[Tinker2]

Frankly I am skeptical that a modern lathe would cut threads similar enough to those used in these old barrels, and plug.

??



Tinker2

 

[jerrywh]

It's impossible to give a safe opinion sight unseen. Original French and Belgian percussion and flint shotgun breech plugs did not seat in the barrel, they just screwed into the bore. I have removed them from guns that were 150 years old and they were in super good condition in every case.

 

[paulvallandigham]

Threads come in different Shapes, with different angles to the thread itself. I was not referring to getting a thread with the correct PITCH.

Compare, for instance, the thread on the main screw on any bench vise, with the threads on the average wood screw.

When dealing with threading the breech of a gun barrel, its important that the Shape of the thread be identical on both parts, so that you get that "bank vault door" kind of "seal", when the parts are screwed together. You are holding back thousands of pounds of pressure when that gun is fired- if only for an instant, so you need to have those threads match Perfectly.

When dealing with OLD barrels, such as described, you are dealing with threads made in other countries, with other equipment, and different ideas on shape. Trying to match Old threads with new equipment is a manure shoot- even for skilled machinists. Its much easier( faster and cheaper) to start anew- and cut both male and female treads on similar equipment.

When I took my machine shop course, I was shown a lot of different screw styles. When later I had a chance to work with a master machinist, he showed me an old gun that had the same Pitch, and the same shape to the threads, but the groove depth was much more shallow on the old threads than we put on the new threads. In this case, cutting the grooves deeper was not a cure, as that would change the diameter of the threaded section, and his male bolt threads would now be too shallow.

Its the old story that you can take off metal, but its darn hard to put it back on.

That is why I am skeptical. :grin:

 

[Tinker2]

Threads come in different Shapes, with different angles to the thread itself. I was not referring to getting a thread with the correct PITCH.

"Compare, for instance, the thread on the main screw on any bench vise"

"When dealing with OLD barrels, such as described, you are dealing with threads made in other countries, with other equipment, and different ideas on shape."

"I had a chance to work with a master machinist, he showed me an old gun that had the same Pitch, and the same shape to the threads, but the groove depth was much more shallow on the old threads than we put on the new threads.":grin:

Paul

OK, now I understand. You are referring to things like the British
Whitworth threads and the like, yes?
I had to look that up. It makes prefect sense now, what you meant.

I see now said the blind man as he picked up his hammer and saw.

Thank you for taking the time to explain it.
I do appreciate it.

Thanks

Tinker2

 

[paulvallandigham]

"...You are referring to things like the British
Whitworth threads and the like, yes?

I had to look that up. I am terrible at remembering trade names, mostly because without a reference book, no one else knows what the heck I am talking about!

My brother has a rifle he restored that has a barrel originally made back in the early 1800- 1st decade. The action and stock work were done in the 1870s or 80s. The threads on that barrel and action were something else. Made in America, but the original barrel, made for a flintlock, had been shortened by cutting off the rear of the barrel. New threads were done in the work done years later. A shoulder was used to protect those "new" threads from gas pressure. There is no way to know who put the gun together, but his equipment for making the threads left something to be desired. No electric powered lathe with an automatic feed, for sure.

I believe that this is a common observation about 19th century metal work. With some early work, the threads may have been made using files. These gunmakers had spent years learning their craft, and were masters at using hand tools. They made their own "screw plates, to thread round stock. Dies to thread stock came later, with taps to thread the female parts.

Its really not until after WWII that you find quality machines widely available in American industry to do these tasks to any degree of accuracy and uniformity.

 

[shortstring]

I would tend to agree with Jerry H. I don't remember seeing an old shotgun with an internal shoulder such as we put in a ML rifle. Now, the patent breeches in the shotguns had an external shoulder that would provide the same seal. It's just after the threads instead of in front of them.

It would certainly be my opinion also that machining such as the machining commonly found & used before the CNC age greatly predates WWII. The back woods gunsmiths of the early 20th & 19th century didn't have access to this tech. but out in the real world of manual machining not much has changed in the last 100 years.

 

[Dave K]

Your right about the manual machines. Any good manual lathe and lathe man can duplicate any thread you want. I just had some duplicated on the late 1700's, 20ga. SxS flinter I put back together. I needed an odd thread that happened to be 3/8"-22 thread.

 

[paulvallandigham]

Dave: Mind sharing what equipment you used, and how you did it?

Thanks.

 

[jerrywh]

Personally. I have never seen a thread I could not duplicate. It's just a matter of grinding the tool to match the existing thread. Most 18th century threads are the same as modern pitches either American or metric but the threads are rounded. To think otherwise is to say we do not have the ability to replicate stuff that was done 200 years ago. No offence intended but that is ridiculous.
we have EDM- plasma- CNC- Laser. We can do almost anything. Could they make a star shaped draw plate with holes .030 in diameter in 1800. I think not.
At the risk of my reputation--The fit of breech plugs is highly over emphasized. Yes they must fit well and tight but that's it in my opinion. None of us or our kids will ever shoot a black powder gun long enough to rust out a breech plug. Scientifically speaking the bore is much more likely to fail than the breech plug. A breech plug that is 1/2" long and has a 90% thread is at least twice as strong as the barrel wall and there is only about 1/3 the pressure applied to it.
I have discussed this with two of the best barrel makers in the country and they agree.
Has anybody here ever seen a breech plug blow out??? I don't know anybody who has.

 

[Vaino]

I agree w/ Jerry. When a "blownup" BP gun is shown, the bbl blows but the breech plug is still intact and this is due to much less force exerted on the breechplug face because only the area of the bore times the pressure determines the total force on the breechplug. The bbl encounters pressure from the circumference of the bore {360 degrees} and this area is much greater than that exerted on the breechplug face. I for one would like to see the plug thread length reduced to 3/8" in lieu of the present 1/2"-17/32" as presently offered by the bbl makers which is done for liablity concerns.....Fred

 

[jerrywh]

Any engineer will tell you that three [FULL] threads gives maximum strength. The trouble is one must make sure he can get three FULL threads on a 3/8' plug. I know the rules but I'm still a little creepy on the 3/8" plug. I always use a 1/2" plug and cut a U shaped slot in the side for the touch hole. It reduces the thread count on that side but the plug would have to turn sideways in the bore to come out. In order for the plug to turn sideways the barrel would have to fail. It aint gonna happen my friends. This puts the touch hole back to 3/8 from the end of the barrel. I recently tested a barrel made of 1117 steel with a wall of .037 6" from the breech with 150 grains of FFG goex and a .054 prb. I could not blow it up. It was a 28ga. The breech plugs was a .605 x 24 tpi. Yes I make my own taps.
PS. I have some original plugs that are made the same way.

 

[paulvallandigham]

I have only seen one picture of a breech blown, and the breechplug was still intact. This gun was apparently overloaded with SMOKELESS powder, BTW. The Barrel split right down past the threaded breech, leaving the breech plug and its threads exposed. The picture was not detailed(close) enough to know if a shoulder was used or not.

Plugs blowing from shotgun barrels are a different breed than when discussing rifle barrels. You are more likely to get a failure in those thin, round shotgun barrels, than in most rifle barrels.

We certainly have the kind of equipment today to replicate any shape of threads, and any pitch.

I was interested in what equipment YOU used. I knew a couple of master machinists who could grind cutting bits to extraordinary close tolerance using their experience, and " eye " only. Only when they had the bit "finished", did they then double check it with calipers, or micrometers. They usually did not have to change anything, a fact of constant amazement to the other machinists with whom they worked. :hatsoff:

 

[jerrywh]

shotguns only have about 1/3 to 1/4 the chamber pressure of rifles if loaded proerly. Even on modern shotguns. Check out the balistics in the reloading books. A 28 gauge black powder shotgun loaded with a standard charge has a pressure of 10,000 psi. or less. A 54 cal. rifle with a prb is probably double that if my memory serves me correctly. In the bigger gauges the pressure falls off very rapidly as the shot moves up the barrel. I have specs on all this stuff but i'm too busy to look it up right now.
I am a firearms engraver by profession and can grind tools to fit under a microscope if need be. If you can inlay a .002 gold wire in script matching a thread is no problem.
I'm not all that special a lot of guys can do that in my profesion and others. A friend of mine is a microscopic welder. He can weld two .010 wires together.

 

[Birddog6]

If you talk to Navy Arms tech support, they will tell you that a load of Shot has much more chamber pressure than a roundball the same caliber of the barrel. They state the shot bunches & thus causes a tighter seal & harder to move than a patched round ball, which lets gas escape around the ball.

I called them years ago as I had a Navy Arms double barrel shotgun & wanted to shoot a round ball from it, so called them to get the specifics on the shotgun.

Keith lisle

 

[tnguy]

sorry it has taken me a bit to get back to this. thanks for the info guys. these barrels both were cut, squared, and re breeched with new plugs and matching threads. both of them have good bores as well. the work was done by an experienced machinist as well as muzzleloader smith.

 

[jerrywh]

Read this. I have more if required. http://books.google.com/books?id=D...ck powder shotgun pressures pressure&f=false