Selecting a Breach Plug

[k.jacobfrost]

I'm wondering how to go about selecting and installing a breach plug. The barrels we are using are about .50 with a 1/4" wall thickness and are smoothbore. What size plug would be recommended? We have not tapped threads into the barrel yet, so I would figure we have fairly flexible options.

Thanks

 

[Bountyhunter]

If I were you, I'd take a barrel and run up to Denver to the Colorado School of Trades, I believe it is on Hoyt Ave, and go into the gunsmithing shop and ask them, or run down to Trinidad to the Junior College and ask them, both of those schools are top gunsmithing schools and they could help you much more than we, not being able to see what you have. That way, the instructors could see exactly what you have and advise you acordingly.

What is the source of this tubing? Do you know the metal classification?

Keep us posted, do you have pictures?

 

[k.jacobfrost]

If I were you, I'd take a barrel and run up to Denver to the Colorado School of Trades, I believe it is on Hoyt Ave, and go into the gunsmithing shop and ask them, or run down to Trinidad to the Junior College and ask them, both of those schools are top gunsmithing schools and they could help you much more than we, not being able to see what you have. That way, the instructors could see exactly what you have and advise you accordingly.

What is the source of this tubing? Do you know the metal classification?

Keep us posted, do you have pictures?

Seeing that I am now living in Broomfield, Co. Taking it to The school of traids could be an option.

We got the tubing from Metal Express ,unfortunately there web site is out of date, but they are vary helpful and willing to work with you. I made my order by calling the California office.

This is the info I have on the tubing: c1026 dom ew stl tube a513 t5.

I do not have any pictures at this time, but we are making a few wheellock pistols. So far we have cut out ruff stocks and purchased the barrels. I will be posting photos latter this week.

 

[Zonie]

The c1026 dom ew stl tube you have is made out of 1026 steel. It is NOT seamless tubing even though it may look like seamless tubing.

The "dom" stands for "drawn over mandrel", the "ew" means it is rolled and Electrically Welded, usually using resistance welding.

The "dom" part means that after it is welded, it is drawn (or sized) over a mandrel which smooths out the weld (often totally hiding it) and creates a smooth correctly sized tube.

I cannot tell you not to use it for a gun barrel but I am not a big fan of using real seamless tubing (which does not have weld joints it it) without haveing full certification sheets with it.

There is no way I would use resistance welded tubing for one of my gunbarrels unless I was making a non firing wall hanger.

zonie

 

[subknave]

What kind of steel is usually used in a gun barrel?

 

[Zonie]

Most muzzleloaders use low carbon steel such as 1018, 1112, 1030, 12L14 and such.

Although these steels are not very strong (54,000-70,000 PSI Yield strength for cold drawn material) they are suitable for Black Powder pressures. The key here is that they are normally made out of solid bar stock, not welded tubing.

Modern cartridge guns usually use high strength alloy steels with strengths in the 130,000-260,000 PSI Yield strength zone.

I might point out that the strength of a part is based on its crossectional area in square inches so these big numbers don't mean a part made of the material can be subjected to a internal pressure of 130,000 PSI.
If for instance you had a gunbarrel which was 7/8 inch in diameter it would have a crossectional area of .601 square inches. If it had a bore of 1/2 inch, the bore removes .196 square inches. This leaves a crossectional area of .405 square inches.

If this barrel was made out of a steel with a yield strength of 70,000 PSI it would be able to accept a load up to .405 square inches X 70000 pounds per square inch, or 28348 actual pounds of load without yielding (permanently deforming).

When dealing with internal pressures, the formula used to determine the safe strength is much more complicated than this example but hopefully this example makes some sense to folks.
I might add that when dealing with life/death designs a safety factor of 2 to 4 is used to assure that someone doesn't get killed when they use the part.

zonie