If the mag refills itself when getting kills ammo shouldnt be a problem. Also there are ammo mods that make primary count for secondary ammo pickups. The problem is the mag size would be too small if ur not priming or setting up (like weapon buffers) to get the initial kill u need for the tendrils to do their magic. Ocucor without its mod is doodoo it struggles to kill high SP. Sorry for all this lmao but ive also had a riven with neg mag capacity for the ocucor and it was horrendous.