I cast two cannons today. I actually made three in wax but I had some difficulty trying to fit them into my 5×7 inch casting flask. The cannons are 5 5/8 inches long, but the rubber base for the flask uses 1 1/4 inch of space for the button reservoir. I also require a half inch of investment at the top of the flask, and this leaves only 5 1/4 inches of space inside the flask. I can just make it if I angle the cannon in the flask to get a little extra height. Physics!
I’ll actually have better luck with my 4×7 inch flask. The 4 inch rubber base only requires 1 inch of reservoir space so I pick up just enough room.
The cannons weight about 330 grams each. The would need to be re-bored if I wanted them to actually fire cannon balls.
The pictures below show how I made the silicone mould for my master. I was actually casting Supergirl at the same time, so the cannons were in the same flask as the upper part of Supergirl.