My Lyman GPR Misfires

[coloradoclyde]

Don't tighten the lock to tight with the lock bolt, you might be binding it.

That was my first thought.. :thumbsup:

 

[Flint62Smoothie]

When I shot cap guns, after seating the cap, I’d lower the hammer SLOWLY down onto the cap and would push down hard on the hammer to ensure the cap was fully pressed down and seated on the nipple.

When the cap is not fully seated, some of the energy in the hammer can be lost to just seating the cap further down onto the nipple. Try it!

 

[coloradoclyde]

When I shot cap guns, after seating the cap, I’d lower the hammer SLOWLY down onto the cap and would push down hard on the hammer to ensure the cap was fully pressed down and seated on the nipple.

When the cap is not fully seated, some of the energy in the hammer can be lost to just seating the cap further down onto the nipple. Try it!

You are correct, I use my thumb to make sure the cap seats...As the nipple wears out from repeated hammer blows it begins to "mushroom" making the caps fit tighter and tighter, not allowing them to be fully seated.
This can be remedied by replacing the nipple or filing/sanding it round again...a somewhat delicate process.

 

[Rifleman1776]

Not much I can add with all the good advice given so far.
But, from here it smells like a bad nipple/cap fit issue to me. The nipple can be turned down by chucking and holding a file or good sandpaper against it for a few seconds.
As for tightening the screw holding the lockplate, as others have said, do not overtighten :shake: . If not tightened you can put a bit of beeswax on the ends of the threads. That stuff is both a lube and kinda 'sticky', it will help hold the screw from loosening. Good luck, carry on and let us know what happens.

 

[Elkeater]

Have you used a pipe cleaner with the nipple off?

Run one thru the hole under the nipple.

 

[necchi]

Have you used a pipe cleaner with the nipple off?

Run one thru the hole under the nipple.

If you read the thread,, the problem he has is the cap not going off.
When his cap goes off,, the gun goes off.
When the cap does not fire,, the gun does not fire.
Reading is helpful.

 

[54ball]

This is a very simple problem.

The cap is not seated properly on the nipple.

This is why it takes multiple strikes of the hammer to fire. What's happening is the hammer has to "hammer" down the nipple until it's seated, then it will fire.

Most of the time a capper will not seat the nipple correctly.

This is what I do....

Remember a percussion cap is ignited by percussion, NOT compression. After I place the cap on the nipple, I make sure it is seated by gently pressing the cap down.

There's not really room to do this with say, your thumb on a GPR in half cock because the hammer rests so close to the nipple.

This is what I do with the Great Plains. Realizing any firearm is inherently dangerous, I mind the muzzle. On halfcock I cap the nipple. Then I gently let the hammer down on the cap and gently press the hammer, seating the nipple. After the the cap is set on the nipple I bring the hammer back to half cock.

When you cap a rifle....always be in control of the muzzle have it down range or pointed to a safe place.

Another thing that may help is gently dressing the nipple with a small file and polishing it with fire Emory or sandpaper. One thing you do not want is the nipple to be too loose.

 

[Newtire]

Found the same to be my problem after reading this thread. My hammer was dragging on that screw, only mine is a flintlock and sometimes no spark! Thanks to this thread, I found it. I have a caplock Traditions that had a problem that a shoulder on the inside of the hammer was hitting the top of the lockplate and stopping just short of crunching the cap. A guy on Cast boolits solved that one for me. Great information on these sites.

 

[Billy Boy]

I have a GPR in 54, percussion, had same prob. On mine, the fly was protruding emough to intefere with hammer rotation when tripped by the sear. I stoned and reshaped the fly (it has a long and a shorter face) until it didn't interfere, much faster lock time, much harded happer strike, NO misfires. Also, there is a recess in the Lyman breech face that collects manure, keeps it. A 36 cal. fouling scraper fits fine, get rid of the stuff. This amounted to a muddy spot in the breech that the charge sits on. All is good now, one of my favorite rifles.

 

[Ames]

With mine the factory mortise set the barrel too far forward. Or, they mortised the lock too far back. After 2 years of frustrations with nipples and caps I saw the hammer was just a bit back of center of the nipple.
I went back in the mortise of the butt of the barrel and the end of the tang for a little wood doctoring. Slid the whole operation back 1/16 of an inch the get the hammer centered on the nipple front to back.
Now it fires 100%.