I'm sorry it took me so long to reply, but I actually did come up with a solution. The standard method for syncing projectiles in networked multiplayer games is to provide the same velocity, position, and time to each client, as I've stated. I can effectively do the same thing with projectiles...
I have a strange question. It's strange because I don't need a correct answer. I need an answer that seems correct and leads to predictable results. I'm making a multiplayer computer game where the players fire cannons in outer space. The cannon shells will move through the gravitational fields...