Think Nailgun, not Railgun
Think light railgun for soft targets, with a missile launcher for the heavy stuff.
Tanks, helicopters & putting holes in thick cover are covered by the missiles while people, light vehicles & thin cover get shredded by the Nailgun. In fact, with a millimeter-band radar, or a datalink tying into one, you've got a point-defence gun for handheld, infantry-fired anti-vehicle missiles.
Although as I recall, with this type of weapon, it's heat dissipation that's the real problem...
Biting the hand that feeds IT
