Lyman Great Plains Rifle Issues

[Jake20]

Hello, I picked up a Lyman Great Plains rifle (45 cal) some time back, and it's got some things going on with it that I'm not sure about. I am extremely new to muzzleloaders, so I'm not sure if these things are actually issues, or if they're normal. Googling the issues hasn't been much help.

The first issue is that you cannot cock the hammer until you pull the rear trigger to the first "click" position. The second issue is that when fully cocked, the hammer can be dropped by pushing forwards on it (push off).

Is this normal? It seems like the hammer push off would be a safety issue.

 

[leadhoarder]

That is not normal operation. It should cock without setting the trigger and push off is never good.

 

[Stykbow]

Yeah, that ain’t good. Hopefully some of the local experts will chime in with some help. A word of advice though. Take it out and post some well lit pics so they can inspect it the best they can across the internet.

 

[Jake20]

That's kind of what I figured. Yeah, I'll take some good picture here in a little bit when I get home and get them posted.

 

[Walkingeagle]

See that little screw between the two triggers? It is screwed in too far. Back it out and both issues will greatly improve. BTW, don’t worry about it accidentally coming out when you are adjusting, just put it back in a couple threads, you cannot do any damage.
Walk

 

[B P Maniac Shooter]

What does the lock do when its off the gun?
Could be the wood is affecting the trigger.

Just thinking out loud.......

 

[golden sky]

picture? have you taken it apart yet?

 

[Jake20]

Alright, new developments. Adjusting the screw between the triggers almost all the way out has done a couple of things. Now, the hammer will not latch at any cock position unless the rear trigger is pulled to the 2nd "click" (pulled all the way back). If it's only pulled to the first like before, the hammer will act like it wants to lock, but will just drop if you release it. The hammer, once locked, does not drop if pushed on.

I also noticed a few things after I removed the trigger guard.

1. That trigger guard is basically a spring. It has to be slightly bent into position. It's under constant tension.

2. Once removed, the adjustment of the screw between the triggers doesn't matter as far as hammer push off is concerned. Even if it's screwed all the way in, the hammer locks tightly into position. It's only when the trigger guard is on that it has issues.

When off the gun, the lock appears to function correctly. Just pulling the hammer back is enough to make it go into half or full cock.

When on the gun, the hammer does not even attempt to lock unless the rear trigger is fully pulled. It does make a clicking noise when lowered back down.

Looking at how the rear trigger sits in the wood, it appears that when not pulled all the way back, it interferes with the lock and prevents the hammer from being cocked. In the picture of the wood, you can see the top of the rear trigger sticking up in the hole where the sear arm goes. It's keeping it pushed up, preventing the hammer from locking. When the rear triggered is pulled, it cannot be seen in that hole, and the lock functions correctly.

Pictures below. Let me know if I need to take more.


Resting

Half cock

Full cock

Wood

Underside

 

[towgunner11h]

I'm inclined to agree with BP Maniac- wood interference. Either from overtightening the lock screws or insufficient inletting.

 

[Walkingeagle]

How tight was the lock bolt? If too tight it will bow and warp the lock plate and wont allow correct function. Regarding trigger guard, a slight bend should be all it takes. Obviously don’t break it.
Walk

 

[deerstalkert]

yellow arrow pointing to heavy compressed wood. it is putting a bow into the plate right at the tumbler.

 

[Grenadier1758]

It is possible that there are three things that may be having an effect on your trigger/lock issues.

I normally only hear one click when setting the triggers, but I don't have a Lyman/Investarms rifle. The click you hear is the set trigger lever catching on the front release trigger lever notch. Pulling the rear set trigger to a set capture effectively lowers the rear set trigger lever so the sear can clear the lever and get to the notches.

The rear set lever is too high and interfering with the sear preventing the sear from entering the full cock notch.

1. The tang bolt may be too tight and pulling the trigger plate up enough to lift the trigger lever. Back it off and tap the tang bolt to see if that helps.

2. The spring that drives the set trigger lever may need to be adjusted to lower the height of the rear set trigger lever.

3. That rear wood screw holding the trigger plate in the stock may be pulling the lock plate. @Jake20 may need to put a shim between the lock plate and the mortise.

The nose of the sear should be square and solidly mated to the full cock notch in the tumbler. The hammer should not be easily pushed out of the full cock notch. The geometry of the nose of the sear and the full cock notch is not a simple touch up. This is more of a job for an experienced muzzleloading gunsmith.

 

[longcruise]

As @deerstalkert pointed out with the yellow arrow, there seems to be wood interference. I see several other impressions in the lock inlet that  might be interference.

 

[Jake20]

I can do some inletting if needed. The lock does not seem to be bowed or really even hitting anything. It fits into the rifle without having to be forced into place, and is flush with the outside wood.

On the trigger, it almost seems like it was made to work like this. I feel like the amount of trigger sticking up and interfering with the sear arm is too much to just be adjusted out of the way with a shim or spring. When the rear trigger is pulled to the first click, the lock works like it should. I don't know if it's supposed to be like this, but when the lock is removed and the rear trigger is in it's resting position, it's just kinda loose in there. It can swing forward freely up until the point that it hits the front trigger.

I took her back apart and got some more pictures.

Set trigger not pulled

Pulled to 1st click

Pulled to 2nd click

Not pulled

(Sorry this one is blurry. I didn't realized it came out this way until I had already reassembled the rifle. I did some minor editing to try to make it a little clearer.)

1st click

2nd click

Trigger recess

With trigger assembly installed.

 

[Grenadier1758]

@Jake20, I can see in your last picture that the trigger plate is too deeply pulled into the trigger mortise. A shim between the trigger plate and the stock will separate the trigger lever and the sear lever.

I did read that you don't think a shim will solve the set trigger issues. I think a shim is worth trying.

 

[MO_E_W]

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[Phil Coffins]

There should not be two clicks to set the triggers, with the triggers out of the gun find that first click and remove it. It maybe as simple as a burr on the plate or rear trigger.

 

[Maven]

One problem with the GPR's double set triggers is the adjustment screw/bolt on the trigger plate is too short to do much [good]. It's an odd thread, but longer ones are available from such places as Dixon's in PA and I'm sure others.

 

[Jake20]

Thanks fellas for the advise. I'll shim up the trigger and see if I can't figure out why there's two clicks whenever I get a little bit of free time this weekend. I'll report back then.

 

[VAN]

Assuming no wood clearance problems, shimming the trigger plate out some should ease the pressure the set trigger blade is putting on the sear bar. Another way I fix most of my guns with that problem is by adding another 4-40 round head machine screw drilled and tapped behind the back set trigger to contact the bottom of the long spring in back. Here is a picture of one I'm about to do. The screw laying on top needs to be placed so it makes contact with the spring and does not interfere with the guard. Then adjust it to take off some mainspring pressure. Sometimes the mounting screw at back on that mainspring is cranked down too tight and easing off slightly will allow the lock to work. The front adjusting screw adjusts the front trigger pull and release point of the set trigger.