That’s irrelevant. Many guns these days are controlled electronically and actually have no sears. They are kept from firing by electronic means. . . And the triggers are in a cockpit somewhere many feet away from the actual firing mechanisms. How do you define a rail gun under the law? Where are those parts in that projectile system? It is entirely possible to build a small capacitor driven, hand-held rail gun that could impel a projectile fast enough to kill. Practical? Someday, most likely yes. Today, not so much.
“Hold on, Mr. Burglar, while I plug in, charge up, and load my railgun. . . It’ll take about fifty seconds or so and please don’t mind the high pitch whining sound. . . and would you mind standing over there, please, aiming is a bit tricky.“WHACK!!!
THUD!“DANG IT, HON! I woulda got him. Why’d you have to hit him with a rolling pin while he was a laughing his dang fool head off? I had this...“
I once designed a firing mechanism for a Science Fiction story I was writing that fired a bullet and rifle mechanism that was based on the early 1970s Daisy caseless ammunition system where the propellant was house in a hollow base of the projectile. The propellant was ignited by the firing of a CO2 (or more efficient) laser beam from the breach which also burned the barrel clean with each shot. It could use a binary fuel that was perfectly safe away from the ignition system, and was sealed until the laser burned through the seal.
A rail gun is not a FIREARM.