go off half-cocked
From the days of flintlock and caplock firearms, where the half-cock position of the hammer was both a rudimentary safety, and the proper position for priming the pan or inserting a percussion cap. The phrase was originally rendered, "to go off at half-cock."
- (idiomatic, colloquial): To take a premature or ill-considered action.
- Make sure none of your men go off half-cocked and ruin this operation.