I printed the cannon by Zheng3 and decided I wanted to make a few improvements. This one is slightly larger although has the same bore diameter. One of the main improvements I made was that I made the breach cap threaded and also threaded the end of the barrel so it is easier to attach the cap. Maybe this will also make it stronger but not sure. I also added a couple more supports between the frames including one at the top to make it slightly more rigid, the cannon barrel also fits a bit tighter. I also made the fuse hole come out at an angle to make it slightly easier to feed the fuse through.

Attached you will find the Openscad file in case you want to modify further as well as 3 printable files. There is a file with all parts as well as a file for just the 2 frame halves and a file for just the barrel/cap. I printed mine with the infill set to 50% on the frame but 100% on the barrel/cap and is the reason I broke them up, not to mention the barrel/cap will likely be worn out before the frame.

I may make more improvements after some testing. I am hoping it will withstand a Black Cat firecracker but we will see. What type of firecrackers have others tried in the original?

UPDATE 5/11: I have updated the cannon barrel and cap based on feedback from a user who tested the cannon (thanks @mikel0142 ). The threads on the barrel and cap have been reversed and I have also added some vent holes in the cap to hopefully help relieve some pressure and avoid the cap threads tearing apart. If this does still happen I expect that only the cap would be damaged now and could be quickly re-printed. I have also split each part into separate files so that you can print only a single piece if needed. I have printed everything but have not been able to test fire it so any feedback is welcome.