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Powder chamber should not be larger than the main bore. Sometimes can be smaller. It would be a bit of a challenge to enlarge the diameter of the powder chamber, given that it it deep inside the barrel. Is the barrel bored from solid, or made up from tubing?
Materials? Obviously there is going to be significant pressure, even if only blanks are fired. Go to .muzzleloadingforum.com, go to the cannon section, and read the collection of horror stories about homemade cannon mishaps. You want quality materials, and sound construction. Keep in mind that many tubular products are actually welded tubes, the welds disappear in finishing.
 
well im just playing with the idea, but id probably want to use a solid tube for the above stateed reasons. what kind of max pressure do these monsters produce? anyone have plans for a homemade tube from solid stock?
 
Max pressure is a factor of powder amount, and ball weight. Too much of either, and you are getting into bad things happening.

The actual amount of pressure that is safe, is going to vary by the design and material.

No fixed answer. Sorry.

A typical safe working load on a Black Powder Rifle Cartridge load will give pressures under 20K psi. Some go over that, and lots don't get to much more than half that.
If you figure out how many square inches you start dealing with on the larger bores, you can see that the amount of pressure is non-trivial.

Lots of plans out there, if you look for them. Lot's of information to be gleaned from the sites of folks making them, too. Read for bore size and outside diameters, and materials.
Read the charge weights and ball sizes as well.

It's not really rocket science, but it's worth being aware, as you go into it.

Cheers
Trev
 
trevj said:
Max pressure is a factor of powder amount, and ball weight. Too much of either, and you are getting into bad things happening.
The actual amount of pressure that is safe, is going to vary by the design and material.........No fixed answer. Sorry.
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Well, there are actually fixed answers, but it takes a little math to determine them correctly. One critical item that you are missing to the complex algorythms used in calculating black-powder pressures is burn-rate, usually defined by grain size. Burn rate is defined as time (in MSec) as a part of the calculation. Simply put, using 400grains of FFFg in a 2 inch (smooth) bore barrel of a given length, pushing a given weight is going to give you peak pressures much faster than the same charge of Fg, or cannon powder.

I used to have a functioning link to a website that included all the formula's to determining a given pressure window once all the required variables have been input. Now I can only find this one, which in of itself is a good read, but I'm not sure if the required formula's are buried in it.

ht tp://stinet.dtic.mil/cgi-bin/GetTRDoc?AD=ADA122264&Location=U2&doc=GetTRDoc.pdf"]http://stinet.dtic.mil/cgi-bin/GetTRDoc?AD=ADA122264&Location=U2&doc=GetTRDoc.pdf
 
As for tubing and sizes most if not all the units I have seen around here are made of seamless tubing ie not welded. Iam not sure how this stuff is made but if you are not sure what you have take it to a machine shop and they will check it out for you. My first toy is made from seamless tubing .75 bore with 1.5 inch od, so wall thickness is good imho. I had a machinist tap the end with a 3/4 fine thread bolt approx 2 inches in and drill a touch hole 1/2 inch ahead of it. It has been fired about 20 times using up to 180gr ffg behind a patched steel ball bearing. it will hit a 2 foot square at 75 yd consistantly, and that is just tied to the sooting bench without proper sifgts.
 
577/450 said:
As for tubing and sizes most if not all the units I have seen around here are made of seamless tubing ie not welded. Iam not sure how this stuff is made but if you are not sure what you have take it to a machine shop and they will check it out for you. My first toy is made from seamless tubing .75 bore with 1.5 inch od, so wall thickness is good imho. I had a machinist tap the end with a 3/4 fine thread bolt approx 2 inches in and drill a touch hole 1/2 inch ahead of it. It has been fired about 20 times using up to 180gr ffg behind a patched steel ball bearing. it will hit a 2 foot square at 75 yd consistantly, and that is just tied to the sooting bench without proper sifgts.
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I sincerely hope that the shop did not thread a .75" bore for a 3/4" NF bolt. Perhaps 7/8"x14 NF?
1 1/2" x 3/4" tube has 3/8" walls; a musket barrel will be thinner than this. I have made musket barrels from stock this size.
Theoretically, seamless tubing is capable of containing black powder smoothbore pressures, assuming that there are no flaws incorporated in the steel. Some cold finished tubing is not seamless - you want to be sure that the material you use is. The supplier should be able to tell you.
I suppose there is no reason that a well threaded breechplug would not be acceptable for a cannon.
I sometimes think that it would be a lot of fun to obtain a piece of demilled 37mm or 40mm cannon barrel, perhaps 30" - 36". A rifled muzzleloading gun would be interesting. Use a projectile with an expanding base, or a sabot.
 
Weapontech said:
Well, there are actually fixed answers, but it takes a little math to determine them correctly. One critical item that you are missing to the complex algorythms used in calculating black-powder pressures is burn-rate, usually defined by grain size.
Click to expand...

That's pretty much what I meant, when I said there are no fixed answers. Gotta know all the variables,and do the math. Correctly, too.

On the plus side, the amount of metal that will safely and repeatably withstand the firing cycle, even at some scary load levels, is less metal than most would figure by looking at it. Case in point for that, is the seemingly paltry amount of metal in a musket or trade gun barrel, compared to some of the rifled barrels for muzzle loaders.

Someone asked about materials.

I wouldn't touch steel tube, on the basis of the seam and the weld thereof, though it is likely perfectly safe. Just a flinch factor thing. Seen a few pictures of seamless or DOM tubes that have come apart in various non-gun uses. I'd look hard at 4130 or 4140 steel round bar solid, and bore it out if I wanted to make a larger bore tube, while I would not feel too hard done by if I were able to come up with some bronze round stock to build a smaller tube. Solid bronze, not sintered bearing stock.

I know of one fellow in the US that is casting bronze gun tubes, in Washington state, and cast worked fine for centuries, with a few exceptions (the ones that blew up).
I'd be really uncomfortable being around a cast iron gun tube, without knowing that it had been properly proofed. Even then.. Cast Iron is too brittle. Some of the modified irons might work, like ductile or Meehanite, but I'd look into it really carefully before I went down that particular path.

Cheers
Trev
 
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