Will a derringer shoot blanks without modification?
 

I've been working on the set of a Western lately, and I noticed that some of the prop guns are blank shooting replicas, where as others are real guns that are only loaded with blanks, but would shoot normal rounds if loaded with them. They're all revolvers.

I know that most rifles take modification to shoot blanks. Will a derringer shoot blanks without modification?

Probably, the only guns that require modification to fire blanks are guns that require recoil or gas to cycle.