Is it possible to cast a quickened Fireball as a bonus action, and also use a bonus action to make an attack with Spiritual Weapon on the same turn?

Question

I started playing like a month ago, and the DM was nice enough to create a character for me and write me into the story. I've never played D&D before, but I told him I wanted to be a glass cannon who blows things up, so he made me a Divine Soul sorcerer at level 13. My Metamagics are Twinned Spell, Quickened Spell, and Careful Spell.

I've been reading up on the rules, and just found out before last session that I can use Quickened Spell to cast fireball as a bonus action and also cast fire bolt as my action for extra damage at the expense of 2 sorcery points. My DM gave me the spiritual weapon and spirit guardians spells. This brings me to my question.

Can I, on turn 1, cast fireball, then cast spiritual weapon as a bonus action, then have the spiritual weapon move to/hit a bad guy - then on my next turn, use Quickened Spell on fireball, cast fire bolt, and have the weapon move to/hit the bad guy?

I honestly don't see why not, as spiritual weapon doesn't require concentration like something like animate objects. But in the Player's Handbook, the rules on bonus-action spells says:

A spell cast with a bonus action is especially swift. You must use a bonus action on your turn, provided that you haven't already taken a bonus action this turn. You can't cast another spell during the same turn, except for a cantrip with a casting time of one action.

The part where it says "provided that you haven't already taken a bonus action this turn" would imply that I can't.

But the part that says "you can't cast another spell during the same turn..." leads me to believe I might be able to, because I am not casting another spell, and I am also not concentrating on it. Like if I cast dominate person and tell the person to attack a bad guy, their attacks are not connected to what I do at all. In my opinion, it's a lot like casting conjure celestial and getting a couatl to cast/attack or dominating a monster.

Answer 1

There can be only one Bonus Action

On your turn you can only take one bonus action:

You can take only one bonus action on your turn, so you must choose which bonus action to use when you have more than one available.

In this case, quickening a spell to cast as a bonus action is the use of your bonus action. Should you do that, then you no longer have a bonus action available to move/attack with spiritual weapon.

You can't cast fireball and spiritual weapon

Unfortunately, the spellcasting rules for how many spells you can cast on a turn preclude you from doing this. If you are casting a levelled spell as a bonus action, you can only cast a cantrip with your action. Both those spells are levelled spells, so you can't cast both in the same turn.

Answer 2

Turn 1

Your first turn does not work as described. The rules for spells with a casting time of 1 bonus action:

A spell cast with a bonus action is especially swift. You must use a bonus action on your turn to cast the spell, provided that you haven't already taken a bonus action this turn. You can't cast another spell during the same turn, except for a cantrip with a casting time of 1 action.

You cannot cast both fireball and spiritual weapon in the same turn, as they are both levelled spells.

What you can do on your first turn is cast spiritual weapon with your bonus action, and cast fire bolt with your action.

Turn 2

The second turn does not work as described. You can only take one bonus action on your turn:

You can take only one bonus action on your turn, so you must choose which bonus action to use when you have more than one available.

For your bonus action, you must choose to either quicken fireball or attack with your spiritual weapon, and you may also use your action to cast fire bolt.

Or, optimally, you cast fireball with your action, attack with your spiritual weapon for your bonus action, and save your sorcery points for another time.

Answer 3

You only have one bonus action

The rules include the following text regarding bonus actions (emphasis mine):

Various class features, spells, and other abilities let you take an additional action on your turn called a bonus action. The Cunning Action feature, for example, allows a rogue to take a bonus action. You can take a bonus action only when a special ability, spell, or other feature of the game states that you can do something as a bonus action. You otherwise don’t have a bonus action to take.

You can take only one bonus action on your turn, so you must choose which bonus action to use when you have more than one available.

You can only use one bonus action, so if you use one to cast a quickened spell, you cannot also use one to move the spiritual weapon.

On casting fireball and spiritual weapon

The section on spells with a casting time of a bonus action states (emphasis mine):

A spell cast with a bonus action is especially swift. You must use a bonus action on your turn to cast the spell, provided that you haven’t already taken a bonus action this turn. You can’t cast another spell during the same turn, except for a cantrip with a casting time of 1 action.

So even though fireball has a casting time of 1 action and spiritual weapon has a casting time of 1 bonus action, they cannot actually be cast on the same turn because fireball is not a cantrip.