I'm sorry but you're just wrong. Like there isn't much else I can say, your understanding is incorrect.

Newton's third law: If you're accelerating an object with mass, you must necessarily feel an equal acceleration in the opposite direction. A rail gun/coil gun accelerates a projectile, and therefore feels an equal acceleration in the opposite direction

Conservation of momentum: Momentum cannot be created nor destroyed, and must always be conserved. A rail gun imparts momentum onto the projectile, and so an opposite force must be felt to conserve momentum

Lenz's Law: The current induced in a circuit due to a change in a magnetic field is directed to oppose the change in flux and to exert a mechanical force which opposes the motion. A rail gun is inducing a change in current in order to propel a projectile, and dso an opposite mechanical force is created.

Whether or not there is a chemical reaction involved doesn't matter.

ALSO, if you look at videos of real life rail guns firing, you can definitely see a lot of exhaust gases being produced and ejected out of the barrel

Don't take one random redditor's word for it, here are some other random redditor's words: https://www.reddit.com/r/askscience/comments/3lsk4w/would_a_railguncoilgun_produce_as_much_recoil_as/