The phrase "hung fire" refers to something that has been delayed or postponed, which can be frustrating for those waiting for an outcome. Antonyms for this phrase would be words that describe actions that are quick, decisive, and produce results. These words could include terms like swift, prompt, immediate, expedient, and decisive. Each of these words conveys a sense of urgency and action, which is the opposite of the slow, waiting nature of something that has "hung fire." By using these antonyms, you can express a sense of momentum and decisiveness in your writing or speech, which can be useful in a variety of contexts.