Why does a railgun recoil if the magnetic force pushes the rails outward?

[Danyon]

Do railguns recoil? and if they do, what force is responsible? When I looked at a basic railgun schematic I noticed that the magnetic field from the rails causes the projectile to accelerate forward and I also noticed that the magnetic field from the projectile should push on the rails outward, perpendicular to the direction of motion of the projectile. This doesn't seem to account for the recoil that would be expected

 

[A.T.]

Do railguns recoil? and if they do, what force is responsible?

Did you check the wiki on rail guns?
https://en.wikipedia.org/wiki/Railgun

It has some references on this:

Some erroneous work has suggested that the recoil force in railguns can be redirected or eliminated; careful theoretical and experimental analysis reveals that the recoil force acts on the breech closure just as in a chemical firearm.[20][21][22][23]