Same muzzle energy for the same build. The lack of air and the gravity are going to impact the effective range.
This is a sort of silly discussion for geeks. But it is a silly day so, why not.
I get what you mean, but the effective destructive power and any distance will be increased in space.
But there has to be a measurable loss of projectile force, just in the launch alone. This would not exist in space.
I think a space railgun would have more power even at launch than would one on Earth.
By the time a projectile on Earth leaves the barrel, it has already lost measurable power from the initial launch.
I think we are both right. We are arguing the same point, just in different terms.
But I do see what you mean.