Casting a somatic spell with a shield

[MarkVIIIMarc]

I was just wondering about the mechanics of casting a spell with a somatic while holding a shield and rapier with no special feats.

I'm thinking you must drop your rapier then cast the spell on one turn.

On another site I saw reference to using a free action (I guess unused movement?) to pick the weapon back up.

[Matrix_Walker]

Yes, you can do that, but keep in mind that you can not cast a spell that way defensively using your reaction (like the Shield Spell).

[Saiga]

5E doesn't have free actions, however it does give a list of ways you can interact with an object as part of your action on your turn. You can only interact with one object on your turn, and drawing, sheathing or picking up a weapon use this object interaction.

It also indicates that interacting with an object is part of the action, not in addition to it: the example it gives is "You normally interact with an object while doing something else, such as when you draw a sword as part of an attack". Picking up a dropped rapier isn't part of casting the spell, so I would say the example you gave does not work.

If it did, that defeats the purpose of the War Caster feat, and the shields with holy symbols.

[Matrix_Walker]

Hmn... I guess I was giving too much for that free object interaction...

[ShneekeyTheLost]

Well, War Caster obviously does the job. Sure, it's a feat, but it also gives you Advantage on Concentration checks which is also going to be extremely useful if you are casting in melee. Seems kinda ideal for you.

Other than that, Eldritch Knight track for Fighter gives you Weapon Bond, letting you recover your weapon as a Bonus action, so you can drop, cast, then pick back up as a bonus action.

[Zalabim]

If it did, that defeats the purpose of the War Caster feat, and the shields with holy symbols.
The purpose of shields with holy symbols is to be holy symbols. War Caster still serves its purpose by letting you cast spells as a reaction. And giving advantage on saves to keep concentration. And enabling the casting of spells as a reaction. Allowing it is not bad for war caster, but requiring war caster is bad for EK and valor bards.

[DanInStreatham]

I think that you can pick up the dropped rapier as part of your attack action next turn. So you don't necessarily lose actions if nothing interferes with you, but you can't move away from your dropped rapier and potentially another creature could pick it up or kick it away from you before your next turn.