Barrel wall thickness

[sc45-70]

Why is it that a small cannon is not considered safe unless the barrel wall thickness at the breech is at least the thickness of the bore?
Yet a large bore shoulder fired(or puntgun)often have a barrel thickness at the breech only 1/4 the bore diameter or less and they are considered safe? Example= a 1 inch bore cannon should have an outside beech diameter of at least 3 inches,but a 4 gauge (1.034 inch)smooth bore often has an outside breech diameter of 1 1/2 inches or less. :hmm:

 

[TheDoubleD]

The one caliber wall thickness rule is taken directly from the N-SSA safety standard for construction of cannons and applies over the breech. It is a one size fits all rule for the types of materials used to make cannons.

They require that all original guns that can not pass inspection and all new made guns have a minimum 3/8 liner made to meet meet minimum standards established by ANSI for 3/8" steel seamless tubing.

Modern steels of which modern guns are made is much stronger than what was available in the age of cannon and can be much thinner. The N-SSA rule has to be written to address old and new.

If you wish to build a cannon with thinner walls you can do it, and even safely, but why would you want to?

Take good look at original cannons and you see the that most have a one caliber wall over the breech.

If you build a cannon with thinner walls your proportions will be off and the cannon won't look right. Remember modern made muzzleloading cannon must replicate a pre1899 cannon to fall under the GCA/NFA antique rule.

Keep in mind the one caliber rule applies to the area over the breech. The mountain howitzer appears to ignore the one caliber rule, the walls of the bore being quite thin. It has a howitzer chamber and one caliber wall thickness over the breech.

When I build a cannon or advise someone on building a cannon I always say, "don't build the cannon for how you will use it, build it for how the next guy will use it!"

If an accident does happen and you have built your gun to established safety procedures, it will be in your defense. If you build to safety standards an accident is much less likely to occur.

 

[sc45-70]

Yes I understand the safty aspect.
It just seems strange that you can shoot your 50 cal. 7/8 inch AF rifle all day, yet if you mount that same barrel on wheels it isn't safe.

 

[KABAR2]

Well if you made the punt gun out of cast iron with the wall thickness described most likely you
would have a handgrenade.....
the punt guns wall thickness is thinner becaued it is made out of a different material wroght iron or steel hence a thinner wall.

 

[TheDoubleD]

Yes I understand the safty aspect.
It just seems strange that you can shoot your 50 cal. 7/8 inch AF rifle all day, yet if you mount that same barrel on wheels it isn't safe.

No we didn't say that. We pointed out that it may not meet published safety guidelines for cannons. That's different.

We are saying if you build a cannon you are better protected from liability if you build to the safety standards.

I saw this gun in South Africa. The piece was made to look like a Boer War field artillery piece that was chambered in 38 spl. There is is no way this gun would meet the safety guidelines. The barrel is a rifled liner. It uses fixed ammo. It is safe. Even had Proof house markings. And it replicates a gun made after 1898. I almost brought it back. I would have needed a ATF Form 6.

This was one scary gun to fire...recoil was brutal.

 

[sc45-70]

:No we didn't say that. We pointed out that it may not meet published safety guidelines for cannons.
I know. I was just jerking your chain!
:rotf:

 

[BillinOregon]

DD: You have a lot more will power than I do. I would have had to bring that Boer field piece home.

 

[Marc Adamchek]

Bill - I wonder if the Whitesmoke guys know about this piece? A small historic model, to be sure, but a working model!

 

[buzz]

the last two cannons i made i made using he NSSA rules as a guideline
these rules have been discussed and hashed over but many exsertsw ad i great margin of saety has been biult into them and that is jsut ok to me
although i never shoot at one of ther events
or dont think i will when or if it is time to pass on the cannon it makes it easier
Again i rather be safe then sorry
by the way neat model