My Lyman GPR Misfires

[rwsjr]

I own a percussion Lyman Great Plains Rifle and it has a fairly consistent problem with misfires and I'm getting tired of it!!

This past ML hunting season I was sitting on stump in the woods in Maine, when I see two Does coming towards me. So I get my GPR up, cocked it, pulled the set trigger, aimed and waited as they came closer and closer. Well they got about 35 yards from me, when the lead Doe (the bigger of the two) turned and stopped giving me a perfect broadside. So I took careful aim and I pulled the trigger. All I heard was "Click" and no boom! The gun misfired....again!! So I re-cocked and tried for a second shot, but they heard the click and bolted. Frankly, I was so sick and tired of this issue that I went out an bought a brand new inline muzzleloader that uses 209 primers.

I have had this issue for a long time. I've tried several different nipples and a lot of different No. 11 caps (magnum, reg and different makes) and nothing helps. Don't get me wrong, its not every time but it happens often enough to where I no longer trust the gun. When it does happen, it usually fires the second time, but sometimes it takes 3 or 4 re-cocks to get the gun to fire. This is definitely a cap/nipple/hammer issue because every time the cap goes off the gun always fires. When I fires its really accurate within 100 yards too!

I'm beginning to think that my hammer may be no good or that its spring needs tightening, I just don't know!

Any suggestions?

Thanks

Bob

 

[Grenadier1758]

I own a percussion Lyman Great Plains Rifle and it has a fairly consistent problem with misfires and I'm getting tired of it!!

...

I have had this issue for a long time. I've tried several different nipples and a lot of different No. 11 caps (magnum, reg and different makes) and nothing helps. Don't get me wrong, its not every time but it happens often enough to where I no longer trust the gun. When it does happen, it usually fires the second time, but sometimes it takes 3 or 4 re-cocks to get the gun to fire. This is definitely a cap/nipple/hammer issue because every time the cap goes off the gun always fires. When I fires its really accurate within 100 yards too!

I'm beginning to think that my hammer may be no good or that its spring needs tightening, I just don't know!

Any suggestions?

Thanks

Bob

The GPR is normally a very reliable firearm. Did this rifle function reliably when it was new?

This is probably not a case of the nipple being mushroomed by too much dry firing. You have tried new nipples and different caps.

Something is happening that is preventing the hammer from striking the nipple and cap hard enough to set the cap off.

Have you taken the lock off and verified that the internal components are free of fouling and operate smoothly?

with the lock out of the gun, does the hammer fall faster than when the lock is installed in the stock?

Are any of the components showing signs of rubbing? I would look for signs of rubbing. The lock may be pulled into the mortise too deep and the tumbler may be rubbing the wood in the stock mortise.

The shaft of the tumbler may have to be smoothed. There may be other internal rubbing of the bridle to the tumbler, slowing the hammer fall.

Does the lock need to be taken apart to clean old hardened grease and oils that are slowing the rotation of the tumbler?

 

[Smokey Plainsman]

So the caps are not going off, correct?

Try Remington #10s and the factory nipple. Mine has never failed to set off the cap, and in at least 200 rounds fired, the only issues I've had is if the chambered breech clogs up after a ton of shooting and probably too much moisture on my wiping patches. Think I've only had 2-3 misfires.

 

[Walkingeagle]

Does the hammer strike the nipple square?

 

[mooman76]

How is the cap fit? If the cap doesn't go on all the way, it will hit the cap and push it forward but not with enough push to set it off. Then it goes off the second hit. This and the other questions need to be answered for us to help.

 

[Katahdin]

is the nipple mushroomed?? lots of sighting in could had pounded it into a mushroom shape and the cap has to be hit several times before it is seated?

 

[Grenadier1758]

Take a look at the recess in the nose of the hammer. There may be debris trapped in there that is making a cushion of sorts between the face of the hammer and the nipple. Make sure the hammer is striking the nipple squarely and the recess does not strike the side of the nipple slowing the hammer as it falls.

The usual culprits are not the problem here. We want to do everything to prevent you from going to a system that will give you problems that we can't solve here.

 

[rwsjr]

I'll try to answer each of your questions.

It always seemed to misfire once in while even when new, but I'd have to say its more often now. Keep in mind this doesn't happen on every shot. Sometimes it'll misfire on 5 straight shots and then it will work fine for 10 or 15 more. It's consistently inconsistent!

Yes, the issue is that the caps sometimes don't go off. If the cap fires, then so does the gun.


None of the nipples (I have a several) that I have seem mushroomed, that I can tell, but I did take a fine file to one anyway and tried to narrow the tip a bit, but it didn't help.

I can't exactly tell if the hammer is hitting square on the Cap but it looks okay.

I have taken the lock off the gun to ensure its not dirty or gritty, but I never tried to operate the lock while its off the gun. I will try that in the day or so. Good point, maybe something is rubbing on the stock slowing down the hammer. I'll also make sure nothing is overly warn.

Lastly, that was the biggest Doe I ever saw and she's getting bigger by the day! Someday I'll get over it.

Thanks for all of you ideas!!!

Bob

 

[mooman76]

Caps and nipples are not always a good fit. They tend to be off a tiny bit so that makes the fit not so good sometimes. Some are tapered, some not, some bigger or smaller than others. I'd say they since you tried different nipples and different caps, that is probably not the cause.

Another thing though, make sure your hammer is going down all the way. Some stop a hair short without the nipple but the force of the spring is enough to push it a little farther when snapped. A small washer or shim can cure that.

 

[Grenadier1758]

Put a cap on the nipple and some transfer marker such as lipstick on the nipple. That's easier than getting the transfer material in the nipple recess. Lower the hammer to the nipple. Cock the hammer and look in the recess. You should see some transfer color on the face of the hammer. If you don't see any color then you have to figure out what is keeping your hammer from striking the nipple.

 

[kurts]

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

 

[Smokey Plainsman]

I was thinking the same thing.

I know on my GPR, with nipple removed, the hammer will go forward much farther when de-cocked. On these particular percussion rifles, the hammer is stopped by the cap and nipple only.

 

[don hepler]

If spent caps get jammed into the cavity of the hammer, it can cushion the blow, and not set off the cap. Sometimes they are difficult to see, with the burned powder deposits.

As others have said, it is critical that the cap must be fully seated down on the nipple.

When I go hunting, I want the bore to be freshly cleaned. I also want the nipple to be clean, and be able to see all way thru the nipple. Generally on a clean dry rifle, I do not bother to fire a cap. However if you do fire a cap, prior to loading, hold the barrel down on a leaf or blades of grass, to insure the cap is blowing all the way thru. If I fire a round, during the day hunting, I will reload and continue hunting, but as soon as I get home, I fully clean the gun, including barrel, nipple and hammer cavity.

A clean, dry rifle with the cap fully seated, should fire every time.

 

[jdw276]

On one of mine I over tightened the lock bolt. Bolt came through about a turn and rubbed the hammer as it fell. This slowed the hammer fall to the point it did not strike the cap hard enough to make it fire but made it feel like a normal hammer fall. 3 out of 5 hits no big bang. I saw the silver look to the screw head from the rubbing against the hammer and blued lock. Undid the bolt, ground it a hair shorter and now no issues.

 

[Zonie]

That's probably worth repeating.

The screw that holds the lock in place passes completely thru the lock plate and comes out behind the hammer.

Looking from the lock side of the gun, the end of this screw can't be seen unless the hammer is pulled completely back past the full cock position.

On mine, even with the hammer pulled fully to the rear I can only see about 1/2 of the end of the screw.

If this screw is screwed in too far in an attempt to make the lock screw "really tight so it don't get lost.", it will protrude thru the lock plate and rub on the hammer.

It doesn't take much of this rubbing to keep the hammer from falling on the cap with its full force.

I suggest removing the lock plate retaining screw from the left side of the gun.
Then, screw it in until a slight amount of resistance is felt as the screw pulls the lock plate snugly into place.
Then, turn the screw about 1/8 of a turn more and call it good.

I have a feeling that after this is done the gun will fire the cap every time.

PS: That screw doesn't have to be very tight.
The fit of the mortise will keep the lock in the right place while the snug lock screw just keeps it from moving out of the mortise.

 

[Grenadier1758]

But if the lock has been over tightened for a few years, the lock may always be pulled too deep in the mortise and a shim may have to be fashioned to move the lock and hammer a little further away from the bottom of the lock mortise.

 

[necchi]

the issue is that the caps sometimes don't go off. If the cap fires, then so does the gun.

Feel yer pain,, been there done that.
Ok,, here's a little tip on how to use a forum with either a current question or just researching archives; when the same answer comes up several times(?) you can kinda bet it's valid,, so,,

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

On one of mine I over tightened the lock bolt,,
,This slowed the hammer fall to the point it did not strike the cap hard enough to make it fire but made it feel like a normal hammer fall.

That's probably worth repeating.
,,PS: That screw doesn't have to be very tight.
The fit of the mortise will keep the lock in the right place while the snug lock screw just keeps it from moving out of the mortise.

Those guy's mean that screw just holds the lock in it's place in the wood,, inch pounds of torque,, like 5 inch pounds.
Ok, you got a problem lock,, it's usually not the lock.
Another issue with those locks is you have to fully de-grease it.
Take the lock out, put some rubber gloves on and spray it down with brake cleaner,, work the action, let it dry, then spray it some more.
Then they need plenty of lubrication,, and I don't mean 3-4 drops of gun oil,, in this case with the "problem lock",, you need to get some oil on them moving parts.
Here's a hint; Put those rubber glove on again and get oil all over that lock, inside/outside, upside down,,shake the oil off till it stops dripping, then put it on a rag and let it sit over night.
Then the next day get a clean rag and wipe all the extra oil off.

Seen it a 100 times,, lock is jammed up with dryed/gummy oil/factory packing grease and the lock bolt is tightened like the rifle is a 50 BMG.
If that all sounds "gruff", well I'm sorry,
:hmm:

 

[rwsjr]

This morning I had a few minutes to take a closer look at the gun.

The hammer seems to be hitting the nipple perfectly and there is nothing stuck underneath it.

As suggested I took the lock out of the gun. It definitely wasn't too tight and it may have even been too loose. The inside of the lock wasn't caked with dirt or overly fouled, but it did look rather "dry", as if some lubrication was needed. So I got some fine oil and put a few drops on the moving parts. Then I cocked and fired the lock quite a few times so the oil got into places that I couldn't see. Then I wiped off the excess and re-installed the lock into the gun. Making sure not to over tighten! Then I test fired the gun using about 8 or 9 caps and there were no misfires! I even put a few caps on rather loosely, meaning I didn't use much force when putting them on the nipple, I kind if just laid them on and these fired also. I don't think these would have fired before.

It looks like that a poorly lubricated lock was causing the misfires. That said, I'm keeping my fingers crossed until I can take rifle down to the range for some real testing.

Thanks for all your input!

 

[necchi]

Well that's a step in the right direction.
Trouble with gun oil (or any oils exposed) is it dry out,, it loses it's viscosity,, it becomes gue not oil.
Putting fresh oil on top of the gue will help temporarily,, but that too will soon become more gue.
Old oil needs to be cleaned off on a regular basis then fresh oil liberally applied.
There is no set schedule,, it all depends on conditions and frequency of use.
Ya gotta get the gue off, and put fresh clean oil on and in,, a lot.
Check those three screws that hold the plate on inside the lock, they need to be tight, if those come just a little loose the fly can tip out of position and jam the lock abruptly just short of a complete hammer fall.

 

[Hawken-Hunter]

I've had this problem too. To fix it, I lightly filed around the head of the nipple to remove the "flattened" part. Now the cap sits properly and fires every time.