Lyman Great Plains Rifle

[Grayson Palmer]

I'm sure this is SOMEWHERE in some forum already. I've read and read and read and can't find THIS answer.
I just got a GPR percussion .54 cal kit (first kit ever)! Looks great, only 1 issue so far.
The trigger pull when assembled is terrible, which I have read about in many other forums and know I may wind up ordering a Davis Deerslayer trigger and/or L&R's replacement lock. That is fine if I wind up having to do that.

BUT...here's what I don't get.
I have the trigger assembly out of the gun. Pulling the set trigger was hard (but I have been able to adjust that). Then pulling the other trigger (once the set trigger is set), is nice and light. I've been able to make it too light, too heavy, and just right. No creep. Just a nice light trigger like you would expect.
So far so good.

But, I don't get what releases the hammer. So, I put the trigger assembly back into the gun and cock the hammer. I can pull the set trigger. Hear a click. And then pull the front trigger which is just right. But then I have to pull it quite a bit farther back and then apply a lot of force...for the bar attached to the front trigger to push up on the sear to release the hammer.
I would have expected some kind of connection between the trigger assembly and lock assembly. Instead, I just wind up pressing hard on that sear until the sear spring/plunger is overcome and the sear is released.
Like...I thought the set trigger would get all the parts aligned to the point that a tad bit more pressure and movement would cause the hammer to fall.

 

[Walkingeagle]

Are you using the set screw between the triggers to adjust the sensitivity? That is what needs adjustment, but the factory screw is slightly too short. Pick up a slightly longer one from hardware store and replace. If problems persist from there you may meed to disassemble and polish the parts then reassemble.
Walk

 

[Grayson Palmer]

Yes. I adjusted the set screw between the triggers. Not sure if mine is longer or what but when I screwed it in farther, the front trigger got REALLY light. I backed it out some and it got back to what I'd call a light trigger. I haven't gotten my weights out to measure but let's just say 1.5 lbs. Works great. I may want to back it out more to make it heavier...don't care about that right now.
The problem is, when the front trigger is tripped, it doesn't do anything to the hammer.

I have to pull the front trigger way back on farther until the bar attached to the front trigger contacts the hammer sear. Then I have to press pretty hard to compress the sear plunger/spring. THEN the hammer falls.

It's like I don't have something hooked up properly.

Thanks for your reply! Looking forward to figuring this out.

 

[longcruise]

You have it hooked up properly. This is a common problem with the GPR. It is not a great trigger for starters and to further exacerbate the problem, the position of the trgger Inletting is not necessarily ideal.

You can improve the performance by Inletting the trigger further back but that might also entail moving the trigger guard back. On the plus side, the tang bolt on the GPR doesn't thread into the trigger plate so you don't need to be concerned about that.

I'm not recommending that you do as I described above though. It would be pretty elaborate. This is one of the problems with kit guns in that all that work done for you is not always correct. With the GPR, there are often many Inlets that are off.

I have never used the deer Slayer trigger so can't speak to that but it might be the simplest solution. The other option is to always use the set trigger.

 

[Grayson Palmer]

Position could be the issue.
Using the set trigger doesn't help. I pull the set trigger and can tell that "worked". Then I pull the front trigger...under a pound now that I've tried it again... But then I have pull the front trigger back another quarter to half an inch before the bar attached to the trigger starts pressing against the hammer sear.
It's just weird. No matter what I have to have the trigger overcome the hammer plunger spring. And that seems to be the hard part. The set trigger has nothing to do with the whole setup (right now on my rifle).
But maybe the hump on the bar attached to the front trigger needs to be moved backward or forward so it's contacting, or nearly contacting, the hammer sear. Right now there's a mile between those two pieces.

 

[Grenadier1758]

Using the set trigger isn't the solution. Its also the problem. The set lever isn't striking the sear with enough force to release the sear from the full cock notch. Then the front lever is so far back that the effort to trip the sear is excessive.

With the triggers removed from the stock, is there an internal adjustment screw that raises and lowers the set trigger lever? You may want to adjust that to raise the set trigger lever by putting more spring tension on the set trigger lever. The triggers may not be inlet deep enough into the stock to properly engage the sear. If you remove the lock, can you see the trigger levers in the hole for the sear lever? If not, then the trigger plate needs to be inlet a bit deeper.

https://www.lymanproducts.com/media/catalog/product/g/r/great_plains_rifle_and_hunter_p2.pdf

Go down to the drawing of the trigger assembly. Screw #56 may not be tightened enough to give energy to the set trigger lever #50. With the triggers unset, tighten the mainspring screw #56 and see it the set trigger raises. Take the lock out and place the trigger plate in its mortise. Look through the hole for the sear. With the triggers removed You should see the lever. Also look at the bottom of the sear hole. The tip of the sear lever may be dragging on the wood. The sear needs to be long enough to clear the trigger levers. In kits, the sear lever over the trigger levers may be too long. If the sear lever is too long, you can either deepen the hole for the sear or shorten the sear lever.

 

[Grayson Palmer]

Ahhh...this is something to think about Grenadier1758.
Yes for sure the front lever is so far back the effort to trip the sear is excessive. Agreed.
I can't figure out how the set lever is supposed to strike the hammer sear though.
Still not got the problem solved in my head but this is another avenue to look at.
Thanks! Going to go look to see if I can see the trigger levers in the hole for the sear lever.

 

[Grenadier1758]

Using the set trigger isn't the solution. Its also the problem. The set lever isn't striking the sear with enough force to release the sear from the full cock notch. Then the front lever is so far back that the effort to trip the sear is excessive.

With the triggers removed from the stock, is there an internal adjustment screw that raises and lowers the set trigger lever? You may want to adjust that to raise the set trigger lever by putting more spring tension on the set trigger lever. The triggers may not be inlet deep enough into the stock to properly engage the sear. If you remove the lock, can you see the trigger levers in the hole for the sear lever? If not, then the trigger plate needs to be inlet a bit deeper.

https://www.lymanproducts.com/media/catalog/product/g/r/great_plains_rifle_and_hunter_p2.pdf

Go down to the drawing of the trigger assembly. Screw #56 may not be tightened enough to give energy to the set trigger lever #50. With the triggers unset, tighten the mainspring screw #56 and see it the set trigger raises. Take the lock out and place the trigger plate in its mortise. Look through the hole for the sear. With the triggers removed You should see the lever. Also look at the bottom of the sear hole. The tip of the sear lever may be dragging on the wood. The sear needs to be long enough to clear the trigger levers. In kits, the sear lever over the trigger levers may be too long. If the sear lever is too long, you can either deepen the hole for the sear or shorten the sear lever.

I added some more details above.

 

[longcruise]

For clarity, I got the impression that the trigger and lock function fine when you set the trigger and pull the front trigger. Is this correct? Does the lock "fire" or drop the hammer when you set the trigger and then pull the front trigger?

 

[Grenadier1758]

For clarity, I got the impression that the trigger and lock function fine when you set the trigger and pull the front trigger. Is this correct? Does the lock "fire" or drop the hammer when you set the trigger and then pull the front trigger?

As I interpreted the problem, no. When the triggers were set, the front trigger would release the set trigger but the released set lever could not release the sear.

 

[Zonie]

I'm sure this is SOMEWHERE in some forum already...

BUT...here's what I don't get.
I have the trigger assembly out of the gun. Pulling the set trigger was hard (but I have been able to adjust that). Then pulling the other trigger (once the set trigger is set), is nice and light. I've been able to make it too light, too heavy, and just right. No creep. Just a nice light trigger like you would expect.
So far so good.

But, I don't get what releases the hammer..

You have set the tension on the rear trigger spring to light.
Yes, that makes it easier to set the triggers but that strong spring must be set stronger than that.

What happens is, the rear trigger, once cocked or set is accelerated by that spring to a high rate of speed when the front trigger releases it. It then uses this momentums energy to slam into the locks sear arm, knocking the nose of the sear out of the full cock notch. If the rear trigger doesn't get enough speed built up, it won't have enough energy to release the sear.
When this happens, you can hear the rear trigger release and slap the sear arm but because there wasn't enough energy to release the sear it remains in the full cock notch. Then, when you continue to pull the front trigger, the sear disengages with the full cock notch, just like it would if you hadn't set the rear trigger and used only the front trigger to fire the gun.

Increase the tension on the rear triggers spring and all will be will.
Well, maybe not "all" because the rear trigger will need more force to get it to set. This is one of the faults of the the GPR and GPH guns.

 

[longcruise]

I looked at my response above and decided that pictures are in order so here we go.

This is an edit made since Zonie made his post above. If the lock is not tripping, he is showing the solution.

First, below, is the ideal location of the two trigger bars when the are both raised to show in the sear hole inside the lock mortice. This is the ideal world and how a builder would most likely want the set triggers to be located. This would also be where the sear would be located when the hammer is cocked.

Now, as an example of how the inletting can be off, this next picture shows where the sear is located in this particular kit when the hammer is cocked.

This is not necessarily a bad thing, but in any relationship of trigger to sear there needs to be considered the distance between the trigger pivot point and the point of contact with the sear. Here is a GPR trigger showing the distance between these two points. First photo shows the point of contact of the front trigger on the sear. This is the trigger you would pull to fire the rifle unset.

The next photo shows the distance between the contact point and the pivot point. Note that if the ruler were exactly oriented with the two points the distance would be 3/4"

That alone is a problem. This should be more like 3/8". Opinions on that vary but most would acknowledge that 3/4" is way too much. This is about leverage. The further the contact point is from the pivot point the harder (heavier) will be the trigger pull.

Then, to compound the problem, there is the matter of the angle of the force of the trigger bar is applied to the sear. The picture below illustrates this. The green line is the angle between the pivot point of the sear and the point where the sear is contacted by the triggers. The pink line drawn from the front trigger bar at a right angle to the sear bar would be about ideal for a direction of the force to be applied.

Notice that drawing that pink line also improved the point on the trigger bar that would contact the sear bar if the direction of force were correct.

The red line approximates the direction of force actually applied by the front trigger bar when pulling the front trigger unset. In this case, rather than push the sear bar at a right angle to the green line, it is actually trying to push the sear bar at an angle back toward the sear pivot point. NOT a good mechanical advantage.

When you combine the two factors of 3/4" between contact and pivot point of the front trigger and the added effort needed to trigger the sear when actually pushing sorta backwards you end up with a very heavy trigger pull.

On this particular rifle, the trigger pull needed to trip the lock when pulled unset is a bit more than 8# !!!!

The blue line is a poor approximation of the direction of force that would be applied by the rear trigger when it is fired set and the bar bounces up to strike the sear bar. As long as this bar is striking with enough force to trigger the lock, it is not too terribly important. In the case of the rifle in these pictures the lock fires very nicely when set.

Another issue that can be encountered with the GPR trigger is the inletting as done by the factory. The picture below shows how the trigger should be inlet so that it is pretty much flush with the wood. If the trigger is inlet deep into the wood it is going to put things out of wack also.

Now, my little colored lines are not perfect but they are very close. This does illustrate clearly why so many GPRs have such a heavy unset trigger pull.

Maybe the Deer Slayer fixes this. If it does then that's the simplest way to fix this condition.

My rifles are intended primarily for hunting. The set trigger has, IMO no advantage over a good single trigger. So, my solution to this problem is to install a single trigger. The one in the pictures below is my own shop made trigger that fits and works very well although the trigger pull on this one is a bit light. I'll be making another and doing some more tinkering to get it where I want it. In any case, the single trigger and the set trigger will be interchangeable on this gun.

The single trigger in the picture, when installed on a different GPR does not reach the sear bar when fully pulled. All due to minor differences in the inletting of the two rifles.

Hope this helps and maybe others will help further clarify this.

 

[Griff4570]

I had the same issue. Mine was not a kit. I put the Davis trigger in. Made a world of difference and works like it should. Well worth the 50 bucks.

 

[longcruise]

It's a shame that after springing $500 to $600 for a rifle or kit that needs a solution to a trigger problem.

It's not like they haven't had time to work it out. My first rifle from around 1980 had the same problem.

But, it has been a good rifle and has taken plenty of game. Always used the set trigger though.

 

[Grayson Palmer]

Wow! THAT is GREAT information. NOW I get it. I'm good to take an educated look at the whole thing now. Don't know it all, but a LOT more than I did a few hours ago. THANK YOU GUYS VERY MUCH.

 

[Grayson Palmer]

For clarity, I got the impression that the trigger and lock function fine when you set the trigger and pull the front trigger. Is this correct? Does the lock "fire" or drop the hammer when you set the trigger and then pull the front trigger?

It doesn't work "properly" when you use the set trigger. Basically the set trigger is doing nothing. It goes click and I'm sure the lever attached to the set trigger flips up weakly. But then you have to pull the front trigger back a quarter inch and pull like 8 or 10 pounds. I *think* I have the answers below. But wanted to reply to your question. Thank you so much for your help.

 

[Grayson Palmer]

So, let me see if this is right. First I need to look at the trigger levers and sear as longcruise provided (THANK YOU FOR YOUR TIME ON THIS longcruise). I have looked at mine briefly but not had enough time to look thoroughly.
Anyway, when you pull the set trigger, the lever that is release flies up. Is it supposed to fly up with enough force/momentum to partially disengage the hammer sear? Does the hammer fall part of the way? And then all that's left to do is pull the front trigger to allow the hammer to fall the rest of the way. I have a herniated disc in my back which means I can only stand about 5 or 10 minutes at a time right now, otherwise I'd be testing to find some of the answers above.

 

[longcruise]

Zonie explained the adjustment needed to make the set bar strike the sear with enough force to trip the hammer.

Anyway, when you pull the set trigger, the lever that is release flies up. Is it supposed to fly up with enough force/momentum to partially disengage the hammer sear? Does the hammer fall part of the way? And then all that's left to do is pull the front trigger to allow the hammer to fall the rest of the way.

Not sure of your question but here is how it works. You pull the rear trigger first until it clicks into engagement with the front trigger. When you pull the front trigger the bar on the rear trigger flys up and hits the sear arm with enough force to trip the hammer. Boom, the gun goes off.

Like Zonie said, if you adjusted the spring that forces the the rear trigger bar to pop up, you may have lightened it up too much. Probably way too much. When you pull the rear trigger to set it, it will be quite hard to pull.

 

[Zonie]

So, let me see if this is right. ...
Anyway, when you pull the set trigger, the lever that is release flies up. Is it supposed to fly up with enough force/momentum to partially disengage the hammer sear? Does the hammer fall part of the way? ...

No. When you pull the front trigger, the released rear trigger must fly up with enough force to totally disengage the hammer.

If things are working right, you should not have to pull the forward trigger again.

 

[Grayson Palmer]

Got it. Yeah I see now. When I set the trigger, then pull the front trigger, the lever from the rear(set) trigger flies up. But not with enough force to disengage the hammer. I'll try making that stronger and will be looking at other advice on positioning as well today. THANKS!
At this point I have enough understanding to see what is SUPPOSED to happen at least.