The Beam Emitter is just all together useless as it is right now.
They really need to take a good look at this augment because it's complete junk right now. An 80% damage reduction is just silly, it turns even the most powerful weapons in the game into a pathetic and useless item.
Not sure what they were thinking with this Augment, but the way it is right now, you're better off just not using it. If you want a beam weapon that doesn't consume ammo, that's pretty much what the Remnant Weapons are. You're better off just crafting one of those instead of trying to alter another weapon to mimic that style. You could put a Vintage Heat Sink on your Eagle to get to where you don't use ammo, but there is currently no way that I'm aware of to turn an Eagle into a Beam Weapon that doesn't use ammo.
Again though, I assume this is intentional because it's assumed that if you want a weapon with those properties, you will simply craft one that's designed that way. If the Beam Emitter is fixed, it will likely just be a fix to the damage and not the ammo properties of the augmentation. Try a Remnant Weapon with Electrical Conduits.. it will absolutely destroy Shields and non armored foes, have a very cool visual effect, and won't use ammo.