shaped charge type 40mm HE grenades would be fine if you have to defend against a heavily armoured killer robot, but ones like this with exposed hydraulic lines

shaped charge type 40mm HE grenades would be fine if you have to defend against a heavily armoured killer robot, but ones like this with exposed hydraulic lines will fall over and curl up after a well placed knife attack, or maybe 12ga flechette rounds from a shotgun if you need a ranged attack.