IIRC, early texts describe the SP-55X as "conventional ammunition". It was only later that they gave this "conventional ammunition" a designation, namely "SP-55X". And those text (one of the early issues of the Chronicle) describes the sniper rifle as a gun that uses gunpowder/propellant and electromagnetic rails to accelerate the round/bullet/projectile. So it sounded more like a hybrid weapon than a "true" rail gun. Later texts haven't bothered to repeat the wording. Now the Chronicle's VF-25G article may clear it up but until then:
http://www.macrossworld.com/mwf/index.php?...st&p=737188
Edit: Correction, they have repeated it in the 1/72 kit manual. It describes the SP-55X using gunpowder/propellant and then gets a boost from the rails.
And everything I've seen calls it a "SSL-9B Dragunov Anti-Armor Sniper Rifle", not "SSL-9B Dragunov Electromagnetic Rail Anti-Armor Sniper Rifle".