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set triggers on a lyman great plains

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got a problem with the set triggers on lyman.. you set the rear trigger then fire it most of time it stop at the half cock ... it will fire every time if you use the front trigger first... could the lock be rubbing on the stock???? thanks michael
 
Check the "fly" on the tumbler to see if it is damaged, broken, missing, Ect. That would be the first place I would check based on the problem you are having. It's not likely that the lock is rubbing on the stock to cause the problem you describe.
 
got a problem with the set triggers on lyman.. you set the rear trigger then fire it most of time it stop at the half cock ... it will fire every time if you use the front trigger first... could the lock be rubbing on the stock???? thanks michael

Take the Lock out and see if it hangs up then. Might be the Lock screw is too tight, it just has to be snug.
 
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no it dont hang up out side the stock.. i try it snug and tight .. some times it goes all the way down sometimes it dont ...
 
The fly looks like a tiny men’s tie, it’s located on the tumbler. The screw in the triggers has nothing to do do with the function of the lock. You need to find a picture of a lock that names the parts so suggests will make since.
 
I would say your sear lever is rubbing on your stock. The Lyman GPR's are notorious about this. Remove the lock and look real close in the hole where your sear lever goes. What you are looking for is a tiny shiny spot in the bottom of the hole. This is where the wood fibers have been compressed by the sear lever, caused by the wood swelling. Take something sharp and scrape the mark away until your triggers again fire the lock reliably. Or you can grind a little off the sear lever as I do.
 
004 (800x600).jpg
 
the fly is in it .. how should the fly be in the tumbler?? found a pic of the fly on lyman web sight.. AMES the fly on mine dont look like the one in pic???
 
does it look like the fly is broke??
 

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does it look like the fly is broke??
It's hard for me to tell with the picture you posted.

To check to see if the fly is working like it should, reassemble the lock. Then, put the hammer at full cock.

Place your thumb on the hammer to control how fast it can fall when the sear is released. The sear is the part that engages the full cock notch. It has an arm that sticks out perpinducular to the lock plate. Pushing up on the arm moves the nose of the sear out of the full cock notch allowing the hammer or cock to fall.

With your thumb ready to resist the force of the falling hammer or cock, push up on the sear arm.

Carefully watch the nose of the sear as the hammer/cock is falling. It will move until it reaches the fly in the tumbler. If the fly is ok, it will block off or cover the half cock notch and the nose of the sear will jump over the fly and the half cock notch.
If the fly doesn't keep the nose of the sear from entering the half cock notch, it must be replaced.

It is ok to shoot the gun using just the front trigger because the force of your finger on the trigger keeps the sear clear of the half cock notch.
It is NOT OK to shoot the gun using the trigger in the set position with the rear trigger set if the fly is not working like it should.
Shooting the gun with the set trigger and a defective fly can break the sear and or the tumbler.

Here is a link to the Lyman site so you can buy a new fly.

https://www.lymanproducts.com/flintlock-lock-replacement-parts

 
The part is #11 in the drawing. The price is $3.81.

The test is simple enough. The fly should move easily in its slot. Look for binding of the fly, the tumbler or the sear. Its worth looking for internal dragging of the sear in the sear recess.
 
does it look like the fly is broke??
Yes, it is as stated by Phil. Knowing what a fly does will help you in the future. When the lock trips via a single tigger the force on the sear is a longer slower one, keeping the sear from falling into half cock. When you use the set trigger, the energy is quick like a mouse trap. It starts the tumbler to rotate, but doesn't keep the energy force there long enough to keep it from going into half cock. The fly shape pivots allowing the sear to go across the HC notch when bringing the hammer back, but pivots back when the hammer is going forward keeping the sear out of half cock.
Hope that helps, and the new fly should take care of your problem.
Flintlocklar:D
 
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