Mobs that shoot straight like a blaze

Mobs that shoot straight like a blaze

My apologies for my not-so-clean English.

I'm currently creating a mob like a blaze. I want it to fire custom projectiles that I've created. So far, everything's going well. The problem in the game is that it doesn't really go straight. It fixes the player well. It shoots towards them, but the projectiles don't go straight. I disabled the gravity of the projectiles, and yet it fires sideways, never straight.

My projectile can be fired by the player, so I'm trying it, and I aim straight.