Projectile Attack

Yes, just use if statements. I am not giving code, but here is an example;

    @Override
    public void attackEntityWithRangedAttack(LivingEntity target, float distanceFactor) {
        ProjectileItemEntity entity;
        if (this.getHealth() >= 7) {
            entity = new ProjectileEntity1(this.world, this);
        } else {
            entity = new ProjectileEntity2(this.world, this, true);
        }
    }

attackEntityWithRangedAttack

This method, provided by IRangedAttackMob, allows the entity to "shoot". Doesn't your ranged mob have this method in the class?

Lol, send over the entire entity class, preferably in a git/pastebin. What Minecraft version are you using/