1999-03-01-01:21:03 Juergen Leising:
> just for interest - can somebody please explain to me, what a "hair trigger"
> is?
In common usage, it describes something that's easy to set off, a delicate
sensor, etc. In this instance, someone was using the phrase to claim that the
mailing list is too sensitive to email bouncing, and ends up unsubscribing
users for brief transient problems.
Originally the term came from certain premium quality firearms, including
target rifles and duelling pistols (and probably some other specialty arms),
where a hair trigger was basically a second-level trigger.
A trigger releases the hammer, allowing a strong spring to drive the hammer
into some ignition mechanism and set off a firearm. For reliable and accurate
operation, it's desireable to have a very strong main spring, so the hammer
hits hard and fast. But with a very strong main spring, the pressure the
hammer sear (the catch that the trigger holds up) applies against the trigger
is very strong, which means the friction of the trigger rubbing across the
hammer sear is very strong, which means that you have a stiff trigger pull
--- you have to pull on the trigger really hard, against a resistance. And
_that_ --- having a stiff trigger --- is bad for accuracy, since it forces
you to strain to release the trigger, which can throw your point of aim off.
The ideal accurate trigger has as close as possible to zero release pressure,
so you can't really tell exactly when you're pressing hard enough to make it
go off. To address this conflict, they came up with a gizmo called a hair
trigger. The hammer is cocked by pulling it back, then the _trigger_ is cocked
by pushing it forward; all that pulling the trigger back has to do is release
a light-weight internal clockwork which in turn releases the hammer. Hair
triggers may have been good for accuracy in ideal conditions, when used by
experts, but they have acquired a reputation for causing accidents, since they
are so easy to set off by accident.
-Bennett
