I am considering the need for war caster vs. resilient (con) on a wizard who will dual wield light weapons.  There may be times when he needs to cast a spell with S or V,S components as a reaction (e.g., shield, absorb elements, counterspell).  I have seen a lot of discussion about how dropping a weapon (non-action) and picking it up again (free object interaction) can solve the need for a free hand to perform S components without the war caster feat.  However, there are two points that are unclear to me:

1. Can one drop a weapon in time to cast a reaction spell?  I have read that the free object interaction has to occur in conjunction with an action or move but have not seen anything definitive about dropping a weapon to allow for casting a spell with a casting time of reaction.

2. Can the drop and pick up be during the same turn, or does the pick up need to occur on the following turn?  I think this would be dependent on whether a free object interaction had already occurred during the current turn or if manipulating a focus or component pouch would count as a free object interaction (assuming one was casting a spell with S,M or V,S,M components).

1. Dropping a weapon is not defined in the rules so it will be up to DM to determine if it can be done before a reaction's trigger.

2. They can be done on the same turn.

As Plaguescarred said whether you can drop a held object as part of a reaction is up to the DM. The free object interaction is something done on your turn but dropping a held item is not a free object interaction so it is not as clearly bound to your turn.

Also, a word of warning. If your DM allows you to drop a held object as part of a reaction doing so can have some serious drawbacks. Because it was dropped outside of your turn you would not be able to pick it back up after finishing your reaction. An intelligent adversary could then use their turn to pick up what you dropped or do something else to make it inaccessible.

Tha

Quote from Plaguescarred >>

1. Dropping a weapon is not defined in the rules so it will be up to DM to determine if it can be done before a reaction's trigger.

2. They can be done on the same turn.

 Thanks for the prompt response.  In regard to (2), I assume this works as long as one has not taken one's turn yet since the pick up occurs in conjunction with an action or move.  

1. There shouldn't be a problem ever dropping the weapon at any point. Dropping a weapon isn't an action, it is the opposite, really, it is not-continuing an act. You could get different results from different DMs, as people here have suggested. But, nothing really supports that conclusion that you'd be unable to do this. TLDR: You should be able to drop a held weapon to enable a reaction somatic cast. You just can't do anything about the fact your weapon is now on the ground until your turn again.

2. Drawing or picking up the weapon is your free interact. But dropping it isn't even an interact at all. You can just freely not keep holding it whenever. So you can for sure drop it and pick it back up in the same turn, IF it simply falls at your feet. Don't be surprised though if your DM causes it to clatter into awkward positions from time to time since to release it as no action you are entirely relinquishing control over it and it is free to clatter wherever the DM says it does. Because trying to control where it lands isn't just relinquishing it, that's tossing it, which, well, THAT would be an item interact.

Quote from Xeyd >>

Tha

Quote from Plaguescarred >>

1. Dropping a weapon is not defined in the rules so it will be up to DM to determine if it can be done before a reaction's trigger.

2. They can be done on the same turn.

 Thanks for the prompt response.  In regard to (2), I assume this works as long as one has not taken one's turn yet since the pick up occurs in conjunction with an action or move.  

Picking something up is usually considered to be the object interaction allowed on your turn. However, it is not associated with either action or movement. The object interaction can occur at any time during your turn.

For example, you could drop the item at the start of your turn, cast a spell, pick it up and then move. Or you could move, drop, move, cast, move back to where it was dropped, pick it up and finish movement (assuming you have enough movement).

However, I wouldn't count on a DM allowing dropping an item as part of a reaction. One interpretation is that reactions are already supposed to be very fast responses to some trigger ... a DM might well rule that there is insufficient time in the midst of your reaction to drop something before taking your reaction (i.e. by the time you get the item clear of your hand, your reaction should have already started if not already finished).

The reason some DMs may be reluctant to allow it before is because a reaction is an instant response to a trigger of some kind.

While there are no explicit rules for dropping an item, considering the act just requires opening ones hand that could reasonable fall under the ruling for Other Activities On Your Turn

This is something corroborated by Jeremy Crawford

@DnDMontreal The intent is that letting go of something requires no appreciable effort. But picking it up does.

So it seems reasonable that within the scope of the rules, letting go of something that isn't a shield* doesn't take any action.

* Shields are a good supporting rule for 'it doesn't take an action to drop something' because the rules explicitly state it requires an action to doff a shield. If releasing other items from your hand required an action, they would be detailed as such

Yeah droping a weapon is not specifically listed as one of the things you can do wile Interacting With Objects Around You so some DMs count it toward one's free item interaction and some don't.

Jeremy Crawford also stated he allow it;

@RSIxidor Does dropping an item count as your one use of "interacting with an object," or can you drop an item as a "free/no action."

@JeremyECrawford In most circumstances, I would allow a character to let go of something without using an action.

I view it as the same as ending concentration. That is a good analogy. Both concentration and holding something are similar in that regard, they represent continued effort to keep something happening. 

Concentrating on a spell requires an ongoing continuous effort, which, you are free to just stop doing at any point. It takes no appreciable amount of time, it just stops when you want. Same for holding something. You're applying continuous gripping actions throughout not only your turn, but other people's turns, and holding on takes some amount of continuous applied effort. Just stopping letting go isn't an action, it is the end of a continuous effort. These both should be freely feasible on anyone's turn and at any point.

I think the same is true for dropping prone but maybe that's a topic for a different thread.

Quote from Davyd >>

While there are no explicit rules for dropping an item, considering the act just requires opening ones hand that could reasonable fall under the ruling for Other Activities On Your Turn

This is something corroborated by Jeremy Crawford

@DnDMontreal The intent is that letting go of something requires no appreciable effort. But picking it up does.

So it seems reasonable that within the scope of the rules, letting go of something that isn't a shield* doesn't take any action.

* Shields are a good supporting rule for 'it doesn't take an action to drop something' because the rules explicitly state it requires an action to doff a shield. If releasing other items from your hand required an action, they would be detailed as such

However, that is "Other activity on your turn". OP wants to use it in a reaction, so presumably they want to use it out of their turn.

That said, I also think it should be allowed, just like a move during a reaction should also be allowed to push open an (unlocked) door.