Hello when i read the forums there is talk about the indian canon which seems more common but the only problem is I don't know how to build one. does anyone have any ideas how
It's pretty complicated. To make one that works well will take a few tries. You are better off buying your first set of guns. If you want to try to make your own the 2nd time go ahead. Having guns that don't work sucks, get some good ones.
Plans are available. They are listed as the JC White's rotating gun system. http://www.strikemodels.com/products/cannon-big-gun/