Cannons

So hard to find any background on this topic, so I did not find much helpful information beside the obvious...
There are few factors that I think will determine the effectiveness of the cannon.
First factor: Angle for the maximum range
In a hypothetical situation, suppose all other factors are controlled, including friction, air resistance, velocity, etc. And the only variables that are being altered is the launching angle of the cannon, how will the range of the cannon ball launched be affected? Or otherwise, what angle will give the biggest maximum range for this projectile motion of cannon?

Imagine launching at 30, 45 and 60.

It seems that the launch angle of 45 will result the farthest distance travelled. From what we learned in kinematics, range of a projectile motion will be determined by the product of hang time and Vx. For angle of 30, it had the biggest value for Vx out of the 3 cases, but it's maximum range was limited by its hangtime due to lack of Vy. For angle of 60, it had the biggest value for Vy. Therefore, its hangtime was the greatest out of all three, however, its maximum range was then limited by its Vx, the lowest of all 3. The angle of 45, which did not have the highest value in any categories, had the biggest maximum range because it had a decent value for both the hangtime and also Vx.


Tight Sealing:
For the duct tape that are used to stick together the pieces of pop can, it ensures that first of all, fuel does not leak when we shake the cannon, and secondly to make sure the no force/energy caused by the explosion "escape" from the launch. This is because we want the force caused by the explosion to focus on the "bullet", which would be the paper cup.

Mass of the base:
The mass should not be too light, because the force that causes the cannon ball to fly on its path will cause an equal force on the base of the cannon (opposite force, newton's 3rd law).This is why tanks and cannons are made out of metal as its for resisting the opposite force after launching.

In summary, what will make a better cannon? A combination of high hang time, initial horizontal velocity, little friction and built almost flawlessly.(Completely enclosed taping, a strong base and other factors)