Gauss Cannons and armour

So, Lilia Hitashigano, my character with a Gauss Cannon, a weapon that literally fires a big spike at over three kilometers per second that can rip through metal, and explodes with any object it comes into contact with. -I.E, if it hits a metal wall, goes through it, and hits another wall, it explodes on both of them, albeit a small one.-

My question is, would that be powerful enough to not really care about Grimm armour, or other armour? -Probably not person armour, but Grimm armour?-

-Although this is a Railgun, they basically have the same effect on a target-
https://www.youtube.com/watch?v=O2QqOvFMG_A