"Real-world" design of rail gun?

Question

For example, if the rails are 2 feet long, and the projectile is 1/4 in. wide by 4 in. long.
How many KW are needed to shoot the projectile and not get welded to the rails?
How many KW per X meters per second?
These and other design questions need to be answered.

I do not want data for just ONE unit, I want the math, so I can build small to test and debug, than scale-up as needed

Answer 1

What real world? You've not given any requirements for how fast the projectile has to go. How heavy is the projectile?