I have a question about handling a large ammount of bullets using physx (or other system) in unity. Im building an old style shooter (contra style) where every shoot has a bullet, how can I handle the collision between dozens (or hundreds) of bullets.
Worse yet if another player goes in online how can I know which bullets positions must be sent through the network?
About the handle there are a few ways I use this one (for me the best and fastes one)
I use the particle system 
I have a script that holds all the Vectors (of any of this particles)
and also I don’t use the physics for collision - it is much faster when you check if the bullet hit a bounding box (of a enemy) and then if the bullet hits the mesh (with raycast)
I destroy the bullets after they are out of the screen, but you should have a “life time” for every bullet.
this list of bullets can be synct with other players.
When tyou have a contra style game I don’t think that tere will be ever more than 50bullets at one time so this can be synct over isdn without a problem.
cheers