GPR Lock Problems

[keiths]

I have a GPR percussion rifle in .54 that I built several years ago. I really love the rifle, but every now and then, when using the set trigger, the hammer stops at half-cock. Does anyone have any ideas? If I just use the non-set trigger, it never catches on half cock. I plan to use it for deer in the next month, and I would like to be able to trust the set trigger.
Thanks for any help.

 

[MikeChapin]

It sounds as if the fly is hanging up occasionally. The fly is the small part in the tumbler that allows the sear to ride over the half cock notch when the sear is tapped by the set trigger. When you use just the front trigger, your finger holds the sear clear while the hammer is coming forward.

This might be caused by the fly getting gooed up or a small sliver of wood getting in the works once in a while.

You can either take the lock apart and clean it or you can use spray carborator cleaner with everything in place to get out the gunk. Then give the interior a light coat of Break Free or other lube. That may fix the problem.

To see if there is a problem with a wood sliver or something, look at the area of the inlet around the tumbler. If it looks a little raggity, just scrape it a little with a small chisel or something that will smooth out the wood.

 

[CoyoteJoe]

It could be a trigger issue. The screw which holds the rear of the main spring may be a bit loose and tightening it will apply more power to drive the triggers. There is also a stop screw under that spring which determines where the "power stroke" of the trigger stops and that may also be out of adjustment. But most likely it is a problem with the fly in the tumbler and it may need nothing more than cleaning and lubrication.

 

[twsteven]

I know some have encountered this problem with T/C and CVA rifles. In both cases it can usually be solved by removing the lock and tightening the screws on the inside of the lock plate. At least that would be what I attempted first, other than cleaning and lubing.

 

[shortjack]

I had the same problem in my GPR 50 and it was the fly. I ordered 2 from Lyman rplaced the one in the rifle and kept the other for a spare, its been working great ever since that was 3 years ago.

 

[Zonie]

The GPR I bought used had the same problem.
The fly was missing from the locks tumbler.

I think that may have been the reason it was in almost unused condition. I'm betting the previous owner just got PO'ed and sold it. :grin:

A couple of bucks to Mr Lyman got me a new fly and now it's working great!

zonie

 

[Brawdhead]

A problem I've had with my GPR lock (and described here once or twice before) is that if I use a non-Lyman-brand replacement nipple (which seem to run a tiny fraction of an inch taller than the OEM nipple), the hammer doesn't fall forward far enough to reset the lock for the next cock.

Was driving me nuts, 'cuz when I would take out the barrel and fiddle with the lock, it worked fine. So then I would put the rifle back together expecting the problem to be resolved, and I again couldn't get it to click into cock position after the first shot.

Then I discovered that sometimes if I push down firmly on the hammer, it'll click and I can cock it again. That eventually led me to compare the replacement nipple to the one that came with the GPR.

I couldn't tell for sure from your description whether your problem might be related to mine. If you think it's possible, then try firing it without the nipple. That might help diagnose whether it's an issue of insufficient clearance for hammer travel at the end of the swing.

The GPR I bought used had the same problem.
The fly was missing from the locks tumbler.

I think that may have been the reason it was in almost unused condition. I'm betting the previous owner just got PO'ed and sold it.

The previous owner might have been the one who lost it in the first place while doing some tinkering.

Dan