who needs a fly?

[thatoneguy82]

So I fully understand the need for a fly on a single set trigger such as the lock can't be cocked without the trigger set nor can it be fired by the front trigger when not set. My question is, what necessitates a fly for use with a double set trigger? It seems that with a double set trigger both the front and rear trigger are pushing the sear out of engagement. Any thoughts?

 

[galamb]

On a single set trigger or double set trigger "when set", releasing the trigger causes a spring to flip/push (whatever you want to call it) the trigger bar against the sear which fires the lock.

Since the sear has it's own spring which tries to push it back to it's "normal" position, the fly closes off the half cock "notch" so that the nose of the sear doesn't "hang up" stopping the trigger dead in the half cock position (or break one of the components - most notably the nose of the sear).

With a single trigger it is not necessary since when you squeeze the trigger the tumbler rotates enough (the hammer gets to the fired position) before you can take pressure off the trigger.

It's the very quick action of the (set spring) that requires the fly to do the same function as keeping the trigger "squeezed" for that split second to allow the nose of the sear to glide over the half cock notch...

 

[biliff]

A fly is needed for use with a set trigger because the set trigger bar only momentarily engages the sear (basically just gives it a good slap to nock it out of the full cock notch). Because it does not continually push the sear bar up the sear can engage the half cock notch as the hammer falls. The fly prevents the sear from entering the half cock notch.

 

[thatoneguy82]

Which must be why my late percussion era Leman lock sporting squirrel rifle doesn't even have a falf cock notch. I an effort to make an econo lock they simply omitted it in order to not have to install a fly.

 

[Many Klatch]

None of my flintlocks have set triggers. Flies can cause problems with the functioning of a lock. With just the slightest excuse they can cause a lock to misbehave. The flies in my guns served no purpose so I removed them all.

Many Klatch