Build a bp cannon?

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G-Force24

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Looking for some input here guys, started thinking it would be fun to have either a bp mortar or cannon, probably cannon. i'd like to have it pop can bore size. I've seen some people on the net build them out of pretty thick steel pipe. Would this be safe? Say maybe a couple of 1/4 inch wall pipes epoxied and welded together so its about an inch thick wall at the base and tapering down towards the muzzle?

Am I in the right place for this? Been away from the forum a while
 
I think it would be a terrible idea to use anything other than a monolithic, seamless piece of good quality steel. I've tossed this idea around myself and have never found a good piece of steel pipe the correct size for a popcan or a soup can etc.
 
I recall years ago someone had one. I think he made it from a hydraulic cylinder. Like from a dump truck hoist.
 
We shoot a friend's cannon every year at our local R&G Open House. His is bored for a pop can - bored on a massive lathe from one solid (massive) chunk of round stock that he salvaged from an old sawmill or something. It is an awesome replica of a Civil War cannon (short barrelled, there is a name for it); he had the outside contoured as well and I can only imagine the amount of time that took. We put usually 15-20 1/2 pop cans filled with concrete through it every year, each one pushed with 4oz - 12 oz of 1Fg, depending on how much we have and how well we're getting 'er dialed in... always an expen$ive day. Lots of empty Goex cans on the ground.

The thing is so loud you can hear it from the tops of the mountains on either end of the valley, I've been told from folks up there during our shoots... Lots of fun.

Only been to one other cannon shoot ~10+ years ago and there were folks there using DOM (seamless) tubing in their cannons (3-4" bore). Some shooters had formed the outside shape of the cannon using fiberglass, to look like the real deal.
 
I built a .50 cal cannon in school (machinist school). I can't remember which site it was, but my instructor would only let me build it if I showed him guidelines for cannon construction. Mine was made from mild steel bar and then I bored it out and machined the outside to a contour shape. I think one important guideline was that the metal surrounding the breach had to be twice as thick as the bore diameter, so mine has at least 1" of steel surrounding the breach.
 
I always figured a length of drill-collar would make a functional cannon. It's real steel, already got a hole
in it, and testing for flaws and cracks wouldn't
Be awfull hard to arrange because it's done all the time
anyway.
 
I have 2 built out of old hydraulic pistons. Both are 3/4" bores, but their outside diameters are 1.5" and 2". I shoot either round balls or key drive slugs in wads. They put on quite a show.
 
May pop can bore size is a bit ambitious for a first cannon. Both price and availability. Looking for something for ease of ammo, would cut down bar stock of an inch to 1.5 diameter and about 2 inch length be ok projectiles?

Sorry super new to cannons, have guns galore
 
G-Force24 said:
Looking for some input here guys, started thinking it would be fun to have either a bp mortar or cannon, probably cannon. i'd like to have it pop can bore size. I've seen some people on the net build them out of pretty thick steel pipe. Would this be safe? Say maybe a couple of 1/4 inch wall pipes epoxied and welded together so its about an inch thick wall at the base and tapering down towards the muzzle?

Am I in the right place for this? Been away from the forum a while
Click to expand...

Here is a beer-can / Tennis Ball size Coehorn Mortar I built some time ago. The key to making a good (and safe) one is to always have a powder-chamber properly sized for the calibre of the bore. There is a formula to calculate the proper sized powder chamber - I have it somewhere.
This one with 110 gns of FFg will launch a cement-filled beer can about 100 feet up, and 150 yards out.

Cut Tennis balls open and fill with cement and they go even further.

coehorn-1.jpg
 
G-Force24 said:
...... I've seen some people on the net build them out of pretty thick steel pipe. Would this be safe? Say maybe a couple of 1/4 inch wall pipes epoxied and welded together so its about an inch thick wall at the base and tapering down towards the muzzle?......
Click to expand...

The tubing used for such things is the very thick wall seamless tube that is rated for very high pressure use. Like hydraulic cylinders of the sort 577/450 used for his cannon.

The generic 1/4 inch wall pipe is more often seamed and that stuff is rated for relatively low pressure use only. That's not to say you can't buy proper seamless pipe with 1/4" wall that has a good pressure rating. Just that you don't find it at the typical local steel yard unless they supply a local outfit with such product on a regular basis.

In any event CANNOT glue or weld tubes together and add up the pressure abilities like you're suggesting with the bolded part of the quote above. It don't work like that. The joint left between the tubes that allows you to slip them over each other acts as a slip n' slide separation so any support from the outer tube is reduced by a high factor. And glue isn't a suitable filler either. It flexes more than the metal and fails at much lower shear and tensile loads and will do little good in the sort of shock pressure of a firearm or cannon barrel. You need the tube for the barrel to be ONE PIECE and to be of suitable thickness and a suitably tough grade of steel. Which is where the stock thick wall tubing used for hydraulic cylinders comes in.

That downhole tubing looks pretty nice too.

Don't discount the cost of powder for such things. At up near $30/lb for black powder you're likely only looking at 5 or 6 shots per lb of powder for a pop can size cannon. You may want to consider something a touch more economical such as a golf ball size bore.
 
That drill collar looks pretty nice - I'd imagine it wouldn't be terribly hard to get 3-6 feet of it from somewhere. Seems like there's always a disused bit sitting around yards, just need to figure out who to talk to. I wonder how it takes machining and pressure from firing...
 
my gun is 50mm or 1 7/8ish. I use a hollow base lead slug that pours at about 1.7 pounds. We proofed it with 2 slugs and 1500 gr ffg by weight. did it 3 times , checked carefully no damage. The breech is a h/d pipe cap threaded on to the barrel with the fuse hole drilled into it. We took apiece of 4 inch pipe centered the barrel in it. Then melted about 75 lbs of lead, stood the unit on the muzzle and poured it in, put a bunch of sand in and poured another 50-60lbs of lead in till it was full. when done was about 270-90lbs for the rest see the photo the recoil on this unit is wicked even with all the weight. I use between 750-950 grains of powder per shot. giving 10-12 shots per pound.--------------------------------------AS SAID EARLIER DO NOT USE ANYTHING LESS THAN SEAMLESS STEEL TUBING----------- PROCEED WITH EXTEME CAUTION----------------
I have only been shooting with the group for 8 years, the only injury in the group memory, other than cuts scrapes and minor burns was a broken arm, got drunk and fell over a log. Standard operations, want to drink you are off the line
 
A sleeve around the combustion chamber would be fine, as long as both pieces were made of reasonable steel, and there is no gap between the two- I.e. they would have to both be precision machined to fit together (An interference shrink fit would be better still). I'll get around to building my BP cannon some day- I was just going to get a solid chunk of steel gun drilled, and then machine the barrel contour to whatever I think looks neat.

I suppose this would be a lot easier to accomplish for a machinist than your average garage DIY project...
 
BCRider said:
The tubing used for such things is the very thick wall seamless tube that is rated for very high pressure use. Like hydraulic cylinders of the sort 577/450 used for his cannon.

The generic 1/4 inch wall pipe is more often seamed and that stuff is rated for relatively low pressure use only. That's not to say you can't buy proper seamless pipe with 1/4" wall that has a good pressure rating. Just that you don't find it at the typical local steel yard unless they supply a local outfit with such product on a regular basis.
Click to expand...

Use this website to calculate pressures and pipe sizing. It uses Barlow's formula's which are principally directed at fluid dynamics, but works fine when calculating ballistic equivalents especially with black powder.

htt p://www.engineersedge.com/calculators/pipe_bust_calc.htm

There are a number of other references on the net which will help you through bore, projectile / weight calculations to determine maximum pressures + your added safety factor. I helped a friend build a BP mountain howitzer last year using high pressure pipe and a welded and pinned breech plug. It was the perfect diameter for a tomato-paste can full of concrete.

Here is my golf-ball cannon I built many years ago using similar construction;

1851Gball.jpg


1851LHS.jpg
 
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