D&D 5E (2014) Booming Blade question

[bedir than]

And spellsniper I hope.

Without it, booming blade has a 5' range: so you cannot use it on the PAM opportunity attack.

How does the opportunity attack get Booming Blade? BB has a casting time of 1 Action, not a Reaction.

 

[Olrox17]

How does the opportunity attack get Booming Blade? BB has a casting time of 1 Action, not a Reaction.

With the Warcaster feat.

 

[Charlaquin]

How does the opportunity attack get Booming Blade? BB has a casting time of 1 Action, not a Reaction.

Warcaster.

 

[bedir than]

With the Warcaster feat.

Warcaster.

Grazie

It's interesting that the target of Booming Blade is not the weapon, but a "creature" though it isn't explicitly stated.