Vortex Beater

It fires far faster than the listed use time suggests and it fires wide, with enough scatter that at any real distance a good share of your rounds sail past a small target. On its own schedule, between those bursts, it launches a homing explosive that costs you no extra ammunition and hits considerably harder than a bullet, and that rocket does most of the work against anything with a body worth aiming at. The rocket scatters even more than the bullets do, but since it homes, that barely matters.

This gun is unusual in that its listed use time and velocity describe nothing it actually does. What you see when you hold it is a projectile spawning bullets and rockets on their own hard coded rates and speeds, and none of that responds to attack speed or velocity from modifiers or accessories. Only raw damage and knockback change anything, which is why Unreal, Godly and Demonic all land in the same place as the best roll. Do not spend reforge money chasing anything faster.

It takes bullets and only bullets. The rockets it fires are generated by the weapon, so you cannot load rockets or any other explosive into it, and the Shroomite Helmet that boosts rocket weapons does nothing at all here. That aside, ammunition is close to free: most shots do not consume a round, so a stack lasts through fights that would drain a normal gun dry.

Chlorophyte Bullets are the standard answer, because seeking rounds correct for the scatter exactly when you are moving fast and firing off angle. That describes the whole of the final fight, where you spend most of your time flying sideways and shooting behind you. The rocket helps here too, since its blast damages the same enemy it just struck directly, so a clean hit lands twice.

The Phantasm beats it on a single target and it is not close. This wins when the screen is full, so the pillars, the events around them and any messy invasion favor the gun, and a boss with one hitbox favors the bow. Most players end up carrying both.

The barrel appears to spin up as you hold the trigger, but the animation is a lie and the rate never changes. There is disabled code in the game that would have given it a genuine ramp, which suggests the plan was to make it work the way the bow does. It was shown off under a different name before release, and it is one of only two guns in the game with a working secondary barrel, the other being the Onyx Blaster. The reload click you hear after you stop firing is cosmetic.