at half cock

at half cock

1. Of a gun, with its hammer pulled back half way (as opposed to "full cock," in which the hammer is positioned as far back as possible in order to allow it to be fired with minimal pressure on the trigger). He wasn't going to shoot—his gun was only at half cock.
2. By extension, hastily or impulsively, without proper preparation. I'll admit that I went off at half cock when I sent that angry email before finding out what really happened.
See also: cock, half
Farlex Dictionary of Idioms.

at half cock

when only partly ready. informal
At half cock is used of a firearm with the cock lifted but not moved to the position at which the trigger will act. It is usually found in go off at half cock or go off half-cocked meaning ‘go ahead without making proper preparation and therefore fail’.
See also: cock, half
Farlex Partner Idioms Dictionary
See also:
  • pull a gun
  • pull a gun on (one)
  • in the gun
  • gun-shy
  • hold a gun to (one's) head
  • hold a gun to head
  • hold a gun to someone's head
  • hold/put a gun to somebody's head
  • put a gun to (one's) head
  • Quaker gun
References in periodicals archive
The cylinder was taken out by the hammer being at half cock and the center axis pin removed.
MODEL 1883
The safety does not block the slide, and it may be engaged with the hammer cocked, uncocked, or even at half cock. There is no de cocking function.
ADCO's TT.45: an early look at a newly available selfloading pistol
"They were playing at half cock and it looked to me as if they were here for the beer.
Football: Croats only here for the beer - Craig
But here, it went off at half cock. Melanie Teall did her level best to achieve lift-off, but remained resolutely earthbound.
Culture: Ballet review: Rambert lifts roof with explosive show; Rambert Dance Company Birmingham Hippodrome
And advocate Ron Watson, for Martin Barr, said that if they didn't get the chance to examine them, the case would "go off at half cock".
Fury as butcher Barr's trial is delayed