Don't do the paintball gun, that would be considered animal abuse.
Instead, invest in good quality fencing or a safe run for your chicks. Be aware your cats WILL predate on the chicks. They may even go after adults birds, but at least the adults fight back. I know as we have a feral cat...
I have chickens inside city limits. My property is fenced. Without it, my girls would be all over the neighborhood. Fencing lets them have the safe freedom of a yard without being confined. It's a safer alternative to free range with a lot of benefits.
Another option would be a good-sized run...