Great Plains kit trigger/lock problem

[noahmercy]

Got a longer screw for the trigger mechanism on my GPR percussion gun yesterday. I installed it and adjusted it to where I wanted it. I stuck everything together and tried the trigger. Well, the hammer only drops to half-cock. I wondered if maybe the screw I had installed had something to do with it, so I reinstalled the factory part. No dice, regardless of how far in or out I turn it. :curse:

If I only pull the front trigger the hammer will go all the way forward, but set it will not work. Any ideas? I'm very mechanically inclined, but I can't determine if the front trigger, the set trigger, or the two combined push the sear upwards. If one or more of you kind souls could give me a quick primer on how the Lyman trigger/hammer group works, I may be able to go to the problem and get it taken care of. I already polished the sides of the sear so it rotates on its screw smoothly. Are there any infamous trouble spots with this gun that I should be aware of?

Thanks in advance. I know I can count on the members of this forum for sound advice. :thumbsup:

 

[flaming canvas]

Sounds like the fly is missing or out of alignment.

 

Noah, I'm not familiar with that particular gun, but if it has a set trigger, and works from the front trigger, when not set, but only drops to half cock when set, it sounds like you are missing the fly, or it is hung up. The fly is a little danggly piece that drops down to keep the sear from engaging the half cock notch when using a set trigger. On most guns now they all have flies, but older ones with out set triggers quite often did'nt have them. I don't have a pictue handy, but I'm sure someone else will have one to show you. If you look at the back of your lock, there should be a small piece dangleing in front of where the half cock position is. If you cock the lock you will see the sear slide by it and allow it to block the half cock position, allowing for the snap of the set to allow it to pass halfcock. Hope this helps Bill

 

[Zonie]

More FLY descriptions:

It is located in the tumbler that has the notches for half cock and full cock ground into it.

It is located at the half cock notch

It is very small and can sometimes be broken.

It should move easilly about it's pin or axel.

It is usually on the side of the tumbler that your looking at when you hold the lock in your hand and look at things like the mainspring, but sometimes it is located next to the lockplate.

It is usually held in place by the bridle or bridge like piece that is screwed to the lockplate and covers most of the tumbler. This bridle also has a hole for the tumbler axel to pivot in.

As others have said, if the hammer is all the way down, as you pull it up to the half cock position, the nose of the sear pushes the fly further up and out of the way so when the hammer is slightly lowered, the nose of the sear can enter the half cock notch. You often can't really see the fly when you do this because it is hidden by the nose of the sear.

As you rotate the hammer from half cock to the full cock position, the nose of the sear will jump over the fly and continue up to the full cock notch.
With the hammer in this position, you should see the fly, a very small piece of metal hanging down so that it blocks off the outer (or sometimes the inner) area of the half cock notch. You should be able to easily move it back and forth.

Holding the hammer, and releasing the sear to allow the hammer to slowly fall, you should see the nose of the sear riding against the tumbler until it gets to the half cock notch. At this point it should run into the fly which keeps it from entering the notch.
Letting the hammer down further will cause the sear to jump over the fly and the half cock notch and continue to ride the outside of the tumbler until the hammer hits it's stop.

If the fly is broken, it needs replacing. Sometimes, too much thick oil or grease can keep it from swinging down to get in the sears way and do its job. If this happens, the nose of the sear will enter the half cock notch.

Take a close look at your lock, and you should be able to figure out what the problem is.

 

[LSU TIGER]

The fly is circled in red on this Chamber's lock. You should get the idea after looking at yours.

 

[Darkhorse]

There IS an infamous trouble spot in the GPR that can cause this problem and it is not the fly. If after checking out the fly etc. and everything is there then check your lock mortice.
The GPR is not sealed well and will absorb moisture and swell. The wood inside the mortice swells out and binds against the internals of your lock, most probably the sear bar itself. Look real close for a shiney spot, this will be where the metal is rubbing agains the wood. Chisel this out and then check it. Or put some lipstick on the lock mechanisms and then chisel out whereever it touches.
When you full the front trigger you are manually tripping the sear and allowing the full strength of the spring to drop the hammer. It is a direct disengagement.
When you set the rear trigger, then pull the front, a spring loaded bar springs up and "HITS" the sear bar, this disengages the notches and the hammer falls.
If wood is binding the sear then this hit may not be strong enough to trip the notches.
Just keep this in mind when looking for a solution.
Been there. Done this.

 

[2172]

I had exactly the problem you describe, and got the advice you're getting. Here is what did work for me: clean the innards of the lock till it is just about bone dry. Cock the lock so that the spring guide on the main spring protrudes, and hold it there with a pair of lock pliers. Disassemble the lock, and take the little spring out of the plunger that works the sear. Take about a half of a coil off it...if that doesn't do it, then a whole coil, but be careful..it is possible to take too much off (did it to my Lyman Deerstalker and had to buy new spring)...I suspect that this will work for you...try it after all of the other advice if that advice doesn't work. You are about the third guy to describe this Lyman GPR problem on line...someone can probably give you the other threads..
Hank..ps, someone on another thread mentioned doing lock disassembly over one of those foam trays that fast food comes in...sounds like a great idea..have spent a lot of my time on hands and knees wondering where little bitty parts got to...

 

[noahmercy]

Now this is funny. About five minutes before I booted up my confuser this morning, my friend from next door stopped by with a friend of his who is half Northern Cheyenne. He looked at the lock, turned to me, and in his best deadpan red man voice said, "Heap big fly missing, paleface." :crackup: I've never met this guy before today and these were the first words he uttered.

So, Flaming, Bill, Zonie, Tiger...y'all were right on track. This lock came without a fly installed. The reason I didn't see it was missing is simple...the diagram I was looking at in the owner's manual didn't have it listed in the lock breakdown. I looked at a different diagram and lo and behold, there it was.

Darkhorse, I'll keep that in mind about the wood expanding, but likely it won't be much of a problem here. Inside my house right now it's 28% humidity and a little less than that outside. :shocking: Being as how I'm originally from Florida, I'm painfully familiar with the detrimental effects of high moisture levels on firearms. It's why most of my high-powered modern guns are stainless and synthetic. I do intend to seal the wood that doesn't show on this gun with glass. Non-PC, to be sure, but it should head any problems like you mentioned.

Hank, I do ya' one better...I disassemble over a big magnetic tray! :: Got in the habit when I was a marine mechanic. That was after I dropped a small part in the drink on a mobile call and couldn't finish a minor repair for 7 months due to the part I dropped being out of production. :cry: (Boy I miss turning wrenches for a living...)

Thanks for all your help, fellas! :thumbsup: