Hey Igor,
If you are making a black powder cannon I have some advice. First of
all is the bore. Just under wine bottle cork size is a good size. That
way you don't need to stuff a wad of some sort into the bore, just
shove in a ready made cork. I'm not sure that I would use 1.25
material for a .8 dia bore though. I like 1/2 inch wall thickness just
to be totally sure the cannon will never split. You should ALWAYS use
some sort of plug in the bore because when lighting the fuse there is
a possibility that a spark will fly off the fuse and land in the
cannon bore and set off the charge. I have seen this happen. If the
cannon is just for making noise then a mortar is best. The barrel
points straight up. 6 or 7 inches is plenty long enough for the
barrel. Use a wide base. The cannon will pretty much stay in the same
place. If using corks they will only fly into the air a little way and
sometimes you can catch them when they fall. The type of powder used
matters as far as noise is concerned. Pyrodex is not as loud as just
regular old black powder. I don't know what Pyrodex is made from, I do
know that it is not the same formula as black powder. It is probably
safer or smokes less or something. Use fffg powder. The finer grain
size is louder. Drill a 1/8 hole for the fuse. Make up a little powder
gage for adding powder to the cannon. A pill bottle with a line drawn
on it works well. It is much better to pour the powder into a measure
and then pour from the measure into the cannon. Black powder is ultra
sensitive to the tiniest of sparks so be really careful whenever the
powder can is open. Black powder cannons are lots of fun as noise
makers but you need to make sure that you are always in control of the
cannon and powder. To illustrate the power I have seen a 55 gallon
steel drum placed over a cannon with a .8 bore filled about two inches
deep with powder launch over 40 feet in the air when the cannon went
off. The barrel was open at one end and this end was placed on the
ground and tipped up so the cannon could be placed under the barrel.
The fuse was lit and the barrel was tipped back down so that it rested
firmly on the ground. A paper wad used in the cannon left a big dent
in the drum bottom. Anyway, have fun!
ERS