A character can only cast one leveled spell on their turn. If they cast another spell it must be a cantrip unless they have a special case due to class ability (Twin, Action Surge, etc.). How does this interact with a reaction based leveled spell given this scenario:

Action - Cast leveled spell and target succeeds save

Reaction - cast leveled spell (Silvery Barbs) to force reroll

Is the reaction considered to be happening on your turn disallowing a leveled reaction spell from being used?

All of the reaction spells would usually happen on another PC/NPCs turn (Shield, Absorb Elements, etc.). If you use shield to defend against an opportunity attack, your casting option is only to cast a cantrip, or am I incorrect?

Quote from theHumanChris >>

A character can only cast one leveled spell on their turn.

This is not actually the rule. You can absolutely cast more than one leveled spell a turn. Two of the more common ways are to either have some levels of Fighter and use Action Surge or the infamous Counterspelling a Counterspell.

You can definitely use Silvery Barbs on the same turn as you cast a leveled spell in order to force a reroll for that spell.

A character can only cast one leveled spell on their turn. If they cast another spell it must be a cantrip unless they have a special case due to class ability (Twin, Action Surge, etc.).

Not quite. The rule is specifically related to bonus actions.

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 an action spell + Silvery Barbs is perfectly legal. However, something like Compelled Duel + Silvery Barbs is not legal, as Compelled Duel is a bonus action spell and therefore prevents reaction spells on the same turn.

Ah, so the rule is specific to the casting of a BA spell, not just any spell. I was unaware of that little piece of information, thank you.

It also says, during the same turn. 

So if you cast silvery barb as a reaction, you do that on someone else's turn. 

Yes you are allowed to cast silvery barb, just as you are allowed to cast counter spell, even though you already cast a leveled spell on your turn no matter if it was with an action or bonus action. 

If you are curious about the combination of spells you can cast on your turn, this chart may be helpful.

Quote from kurtrune >>

So if you cast silvery barb as a reaction, you do that on someone else's turn.

You may also use a reaction on your own turn if the trigger is there

Quote from kurtrune >>

 

Yes you are allowed to cast silvery barb, just as you are allowed to cast counter spell, even though you already cast a leveled spell on your turn no matter if it was with an action or bonus action. 

Incorrect.

If it was a bonus action action spell, be it cantrip or levelled, you cannot cast a reaction spell on your turn so you cannot cast counterspell. 

The rule on bonus action spell applies the restriction to all other spells on your turn - be it action or reaction. 

This was the answer to the question I was debating.

edit: just changed wording

Sorry my bad, I misread. :)

Yes on your own turn you can not cast a leveled spell if you already used the bonus action to cast a leveled spell. Was reading round for some reason... You can however cast a leveled spell as a reaction on any others turn. :)

Also, Rogue (Thief) gets an ability at level 17 to get a whole extra turn, rather than a single action.   Two full castings, two full bonus actions, and even resets your Reaction.

The rule for not casting spells other than cantrips after casting a bonus action spell irritates me. It just doesn't make any sense. Bonus action spells are described as being especially swift. So what about casting a bonus action spell makes it so that you cannot also cast an action spell unless it is a cantrip. I get that there can be balance issues with it but this rule needs something changed to make it feel right. At my table I'm not going to enforce it unless a problem comes up. And since I don't currently have a sorcerer playing I don't see what could really go wrong.

In addition to the Sorceror there are a lot of Bonus Action spells.

Misty Step is particularly common and per the rules you are not allowed to misty step and cast Fireball the same round.  You will be letting this happen.

Similarly, Clerics have the Healing Word , Spiritual Weapon, and many others.  You will be letting them use it and a non-cantrip to attack.

This is in no way a Sorceror only issue.