As to your question about recoil.
I describe a gun, of any size, at the moment of firing as a cube with one moveable wall. That moveable was is the projectile. Four of the five remaining immovable walls make up the barrel. The remaining wall is the breech.
To force the projectile out of the barrel the expanding gasses have to push against something - the breech. This is what produces the recoil forces you mentioned.
A railgun “drags” the projectile along as the magnetic current moves from the breech to the muzzle. There is no pushing the projectile.
When I first looked at this concept roughly 20 years ago the biggest technical problem was what to do with all of that energy when it got to the muzzle end of the track. The free release of that energy produced an EMP that you wouldn’t believe!
A railgun offers many tactical advantages. Ability to rapidly change the range. Increased load out. Increased safety. Reduced logistic issues. These are only the first order of magnitude improvements on our side of the weapon.
The impact at the other end of the weapon are VERY interesting. But, that’s for another post on a different venue.
For every action, there is an equal and opposite reaction.
You don’t need high pressure gases to have recoil.
Disconnect an electric motor from its mounts, while it is under load, and you will discover exactly what I’m talking about. When the rails apply force to the projectile, they are shoved back on with equal force.