Linear rifles were the standard anti-mobile suit weapon of the Union and AEU prior to the introduction beam weapons. While they are still kinetic weapons, they are very different from the chemically powered weapons of the HRL. Rather than using the combustion of a fuel source to propel the bullet, a linear rifle, or rail gun uses electricity and magnetic fields.
Instead of a tubular barrel, the rail gun has two conductive rails, parallel to each other. A voltage is applied across the two rails and the projectile is accelerated into the breech as the rails drag it. The projectile forms a conductive path between the two rails and electricity flows from one to the other. A resulting magnetic field tries to separate the two rails but weapon's receiver secures them in place. Unable to spread the rails, the Lorentz Force acts upon the projectile, pushing it out the muzzle of the weapon at great speeds. The projectile must already be in motion before it enters the rails or it will simply fuse in place.