Fly or no Fly

[Mr Peabody]

I thought a fly was used in percussion locks so you could have a half cock position in the Hammer. I'm wrong, my Zouave lock has no fly and has a half cock position on the hammer. Why does this lock work properly but a T/C lock needs a fly?

[M-Tecs]

Not my area of expertise but a fly is required for set triggers to work.

[curdog007]

A fly is not necessary for single trigger use, but one is needed in the tumbler for use with a set trigger.
I have seen very high quality sporting rifles and match rifles with very nice single triggers that were fitted with a fly, also.
However, with correct tumbler geometry, a crisp 4 lb pull won't require one.

[indian joe]

Not my area of expertise but a fly is required for set triggers to work.

got it!!!

[Mr Peabody]

Thanks!

[JMtoolman]

The fly is a small piece that pivots and causes the sear to ride up and over the half cock notch. It then pivots to the rear to allow the sear to stay in the half cock notch. The toolman

[Mr Peabody]

The fly is a small piece that pivots and causes the sear to ride up and over the half cock notch. It then pivots to the rear to allow the sear to stay in the half cock notch. The toolman

I understood that , I wondered why all the locks didn't use them. Now I know

[405grain]

When you have a hammer fired firearm with a double set trigger you need a fly on the hammer to prevent the tip of the sear from accidentally falling into the half cock notch when the gun is fired. On a normal single trigger action the shooters finger depresses the trigger, which retracts the tip of the sear out of the cocking notch on the hammer. The hammer's release and fall happens very quickly: so quickly that generally the shooters finger cannot release the pressure on the trigger before the hammer has fallen. Because the trigger is being momentarily depressed, the half cock notch will rotate passed the tip of the sear without any interaction between the two.

With a double set trigger, the rear trigger has a strong spring, and a portion of the rear trigger is a large lobe. On it's own the rear trigger shouldn't be able to fire the gun when pulled. When the rear trigger is pulled, a detente on the very front of the rear trigger engages a tiny shelf attached to the front trigger. The front trigger has a very light pull, and is only holding the rear trigger from releasing. (If the front trigger is pulled on it's own without setting the rear trigger it can cause the gun to discharge, but the trigger pull from doing it this way would be very high) Once the rear trigger has been pulled until it engages the front trigger the trigger assembly is considered "set".

When the triggers are set it takes very light pressure on the front trigger to release the rear trigger. When the rear trigger is released its heavy spring causes it to rotate rapidly around its pivot. The lobe on the rear trigger strikes the sear, causing the sear to jump off the cocking notch on the hammer and allowing the hammer to fall. The problem here is that this mechanism happens much faster than the human eye can see, or the human hand can respond. Where a finger on the trigger could easily hold the sear off the hammer for the entire hammer fall, the blow from the rear trigger on the sear is over so quickly that the tip of the sear can come back into contact with the hammer as the hammer is still falling. If the tip of the sear rides into the half cock notch as the hammer is falling the results could be a misfire, a broken sear tip, a broken half cock notch, or any combination of the three.

A fly on the hammer is a small piece of metal that prevents the sear tip from entering the half cock notch while the hammer is falling. The fly can rotate out of the way when the hammer is being cocked, but cannot rotate out of the way as the hammer is falling. If the tip of the sear contacts the hammer as the hammer is falling the fly will cause the sear tip to ride over and past the half cock notch. A fly is not necessary on firearms with standard triggers. (All of this is a general statement because there are many types of both single and double set triggers)