You may end up expending a power supply though.
A use once and discard capacitor may be the power supply of choice for a rail gun.
Capacitors are able to discharge much more quickly than batteries and so would be a preferable source of portable power for a rail gun.
But that is where we are heading?All you need is a reliable power source and you have a portable rifle.
Just imagine a portable railgun rifle with special laser sighting in the hands of a sniper.