Can the Lightning Arrow and Conjure Barrage spells be combined in this way?

Question

In the game I DM for, one player is playing a ranger. The player asked me if he would be able to cast the lightning arrow spell, then use the arrow as ammunition for the conjure barrage spell.

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The lightning arrow spell (PHB, p. 255) has a casting time of 1 bonus action, and a duration of "Concentration, up to 1 minute":

The next time you make a ranged weapon attack during the spell’s duration, the weapon’s ammunition, or the weapon itself if it’s a thrown weapon, transforms into a bolt of lightning. Make the attack roll as normal. The target takes 4d8 lightning damage on a hit, or half as much damage on a miss, instead of the weapon’s normal damage.

Whether you hit or miss, each creature within 10 feet of the target must make a Dexterity saving throw. Each of these creatures takes 2d8 lightning damage on a failed save, or half as much damage on a successful one.

The conjure barrage spell (PHB, p. 225) has a casting time of 1 action and a duration of "Instantaneous":

You throw a nonmagical weapon or fire a piece of nonmagical ammunition into the air to create a cone of identical weapons that shoot forward and then disappear. Each creature in a 60-foot cone must succeed on a Dexterity saving throw. A creature takes 3d8 damage on a failed save, or half as much damage on a successful one. The damage type is the same as that of the weapon or ammunition used as a component.

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The rule on bonus-action spellcasting (PHB, p. 202) states:

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.

But then on the next page, it also states in the rules for concentration (p. 203; emphasis mine):

Normal activity, such as moving and attacking, doesn't interfere with concentration. The following factors can break concentration:

• Casting another spell that requires concentration. You lose concentration on a spell if you cast another spell that requires concentration. You can’t concentrate on two spells at once.

Would the ranger be able to cast both spells in the same turn?
I interpret the last quote as meaning that you can cast 2 spells, if 1 requires concentration and the other does not, unless a spell doesn't count as an attack.

If he can't use them in the same round, could he cast lightning arrow, save it until the next round, then use it for conjure barrage?

Answer 1

RAW, a Ranger can't cast two spells requiring spell slots on the same turn, if one is a bonus action.

One must be a cantrip, if the spell being cast as a bonus action uses a spell slot.

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 l action. -PHB 201

Theoretically you could do it over the course of two (or more) rounds, as long as your concentration on lightning arrow holds up.

But it's not going to stack like your player thinks. Lightning arrow says

The next time you make a ranged weapon attack during the spell's duration, ...

Conjure barrage is technically not a ranged weapon attack. It's a spell effect that forces a saving throw. (Emphasis here mine)

You throw a nonmagical weapon or fire a piece of nonmagical ammunition into the air to create a cone

You throw the ammo into the air, not at a potential target.

Answer 2

No AOE combo, for two reasons

Lightning Arrow vs Conjure Barrage

The requirements for Lightning Arrow and Conjure Barrage seem to be at odds. The Lightning Arrow does not become magical until it has been used for an attack:

Make the attack roll as normal.

This requires an attack roll in order to convert the non-magical arrow into a Lightning Arrow.

Because it remains non-magical, that piece of ammunition can be used for Conjure Barrage.

At the next round (so as not to break action economy and spellcasting rules), the non-magical arrow is thrown up in the air where a cone of identical non-magical arrows are sent down up an enemy, requiring a Saving Throw.

Because there has been no "attack roll as normal", Lightning Arrow is not activated and the Conjure Barrage proceeds as normal with standard non-magical ammunition.

Limitations for Casting more than one spell on your turn

Typically, you can only cast an Action cantrip and Bonus Action spell in a single turn(PHB 202), unless you have dipped into Fighter to gain another Action.

Answer 3

Everything previously stated is true. However, I would say this is largely up to the DM's discretion. Technically, anytime an arrow is fired... it's fired into the air. It's up to you how literal you want to be with your interpretation. I agree that it would at least have to be brought together over two turns due to casting rules, but it's your game. If you want to let your player stack the two abilities, let him. If your worried about how it will effect the balance, you could make it clear that you will only allow it as a last ditch effort for when your players are in a tight spot and several PC's are down. Or you could offer it as a special kind of inspiration to that player.

It's important to know the rules, but it's also important for everyone to have fun. At the end of the day, that's what d&d is all about and what every good DM should strive for.

Answer 4

I think that I might disagree with using the same arrow for Conjure Barrage at all.

My interpretation of the rules are the same as stated above, except that by rolling the D20 in the Lightning Arrow spell, I interpret that you have fired the weapon (Can't really fumble an arrow that is locked and loaded). It has transformed to lightning in mid air and returns to form as a spent arrow on the battlefield. Unless the Ranger wants to spend some movement and one action to retrieve the arrow, it cannot be used again in this battle. I believe that the reason that 5E states that it returns to non-magical form is so that it counts towards the number of arrows that you can retrieve after the battle (as opposed to the Conjure Barrage weapon that is lost).