Not only that, but it's not exactly new technology. Railguns used to be the primary armament of starships in the Star Wars galaxy... about 10,000 years ago. There's got to be a reason that no one uses them anymore, even when it would be much cheaper to do so. And I suspect that reason is a combination of ships being too maneuverable, and particle shield tech simply outpacing the ability of mass drivers to inflict damage on something the scale of a capital ship.
They still make good personal arms though. One of the most famous and expensive pistols/rifles in the galaxy is the Verpine Shatter Gun, which is essentially a Mass Effect-style railgun that fires rice-grain sized projectiles at lethal hypersonic velocities. They are also fairly flexible, with a variety of ammunition types available, including fun little tracker rounds that are essentially just a ball of super-light, dust-like nanites that puff into a small dust-splotch on the target and function as a short-ranged tracking device. Bounty hunters all over the galaxy salivate at the thought of getting their various appendages on a genuine Shatter Gun, even if only the more successful ones can actually afford it.