LogFAQs > #985205804

Its been awhile since I played Eternal but IIRC they wanted you to be frequently swapping weapons in every encounter. I think they leaned more into the "each enemy type is more susceptible to a particular weapon, so use the right weapon for the right enemy" strategy. So prioritizing key enemies, with the right weapons, should help you get through fights without running out of ammo. And also closing in for the chainsaw melees is vital too, to help you sustain ammo.