first i would try to disable collision on the cannons, just to see if the cannon balls are colliding with the cannons on launch (physics wont work if you disable collision on the balls)
second i would try what everynone suggested above, just set the rotation of the projectile and use initial velocity,
on my project, i had to add thse 2 IgnoreActor nodes after i spawn the projectile, here CapsuleCollison is your cannon’s collision component, and Self is the cannon
