Bore and projectile sizing for a mini cannon

[Tbone69]

I'm building a small brass blackpowder cannon, approx 10" long. I am following safe cannon design guidelines, i.e. breech is at least as thick as the bore all around. But I am not familiar with how big to make the bore compared to the projectile. Mainly I will use it for salute charges, not projectiles, but I want it to be capable of shooting a projectile if I get the opportunity to do so.

Let's assume I make the bore 0.375" diameter because that matches the scale of the cannon.

1) Would there be any problem shooting 0.350" lead/steel balls out of that size bore? I would use a patch or two to thicken the ball up so that it seals against the sides.

2) or ...Would it be better to load the powder, then a wad, then drop in any size ball that is smaller than the bore? Like a 0.3125" (5/16") steel slingshot ball.

I would think method #1 is better because the ball can't roll out by gravity, but then there is the chance for overpressure and/or getting a ball permanently stuck if there is a misfire.

Appreciate any guidance... thanks

 

[Tbone69]

Also

3) Does my cannon count as an antique? It is lit with a match and/or cannon fuse, not a percussion cap.

4) Would it be legal for me to sell it to somebody in the future, or does that make me a firearm manufacturer and I would need a business license from the CFO?

 

[cdn_army]

Computing bore size:
To compute the proper bore diameter for a given object to be used as a cannon projectile:

Measure the diameter of your perspective projectile. Divide diameter by 39. Multiply the result by 40.

as for #3 and 4 I am not qualified to provide any legal advice, but MY understanding is as long as it use a ''primitive" mode on ignition like a fuse or something similar, it is NOT considered a firearm....i doubt i will be an antique. I would be considered nothing more than an over sized flintlock type. Again keep in my than my understanding/ interpretation of the law has no legal value. Welcome to the cannon club after shooting a cannon even a .50 bmg suddenly lack in WOW factor

 

[mooncoon]

The best that I can offer on legality, is that the gun is not designed to be shot with one hand (therefore not a handgun) and is ignited by a fuse (ie legally a matchlock) and therefore is presumably an antique as per cc84 1(b). Around here most mini cannons are about 50 cal and shoot a .490 patched round ball. A loose ball can roll forward and cause problems. The amount of powder is comparatively small, arond 40 or 50 grains of black. As to wall thickness, the chamber wall of most 12 guage shot guns is about .15" so that if you make your barrel walls markedly thicker than that, you should be relatively safe but that is only an opinion on my part and you need to use your own judgement.

cheers mooncoon

 

[trevj]

Take a look at the sizes of Hornady Swaged round ball or buckshot that are available and size the bore to allow for a layer of cloth as a patch around it, say .010" (ten thousandths).

Lead balls can be drilled into with a ball puller. Think on that if you are worried about a misfire. If you are threading a breech plug into a barrel, build a spare breech plug that has a grease nipple on it. Another option is to thread a small section of the fuse hole so that you could, say, remove a liner or sleeve, and thread a grease nipple in to the threads there. Look at the idea of the flash hole liners, used on ML rifles, and you will see the general principle.
If you are able to make a cannon, then making a threaded in bushing the correct size is also within your capabilities.

Steel balls are prone to ricochet off hard objects. Your call.

Another point worth considering, is that the fouling from BP gets out of hand after a few shots. It affects the smaller bore faster. That is one of the main reasons you see a lot of .45 and .50 cals around, and fewer smaller bores. Not impossible to deal with, but more management potentially required.

Grease guns work well for pushing out 'mystery' loads from ML's.

Oh yeah. Post pictures when you build it, eh!

Cheers
Trev

 

[Tbone69]

Computing bore size:
To compute the proper bore diameter for a given object to be used as a cannon projectile:

Measure the diameter of your perspective projectile. Divide diameter by 39. Multiply the result by 40.

Ok so your bore is around 2.56% bigger than the ball, that makes sense. Just curious where you got that formula from?

Take a look at the sizes of Hornady Swaged round ball or buckshot that are available and size the bore to allow for a layer of cloth as a patch around it, say .010" (ten thousandths).

Lead balls can be drilled into with a ball puller. Think on that if you are worried about a misfire. If you are threading a breech plug into a barrel, build a spare breech plug that has a grease nipple on it. Another option is to thread a small section of the fuse hole so that you could, say, remove a liner or sleeve, and thread a grease nipple in to the threads there. Look at the idea of the flash hole liners, used on ML rifles, and you will see the general principle.
If you are able to make a cannon, then making a threaded in bushing the correct size is also within your capabilities.

Steel balls are prone to ricochet off hard objects. Your call.

Another point worth considering, is that the fouling from BP gets out of hand after a few shots. It affects the smaller bore faster. That is one of the main reasons you see a lot of .45 and .50 cals around, and fewer smaller bores. Not impossible to deal with, but more management potentially required.

Grease guns work well for pushing out 'mystery' loads from ML's.

Thanks for those tips Trev. Lead ball is probably a better choice for those reasons you gave. I'll have to think about a grease nipple attachment, maybe I can make the fuse hole a tapped sleeve.

Is fouling something that I can scrape out on the spot with a brush or wet swab?

Thanks all, you guys are fantastic, will post pics when it's done.