Anyone ever alter their Lyman GP rifle?

[Wingshot]

My go to hunting and shooting flint gun is an older Lyman GPR in .50 cal. I’ve worked out exceptionally accurate loads for range use and hunting and have enjoyed this rifle for many years. That all said I’m curious if anyone has changed out locks or barrels and what kind of performance gains or losses were detected. I hear all the time that the GPR is THE best off the rack production gun of its type and have no reason to disagree, just curious about what other folks have done with theirs.

[Scota4570]

The flash channels in the breech plug is tiny, I have opened them up to get reliable ignition.  The tang is oddly contoured and makes a strange hump back profile, I have altered that.  The trigger and lock parts are rough castings, I have finished them properly.  The result is a better looking, more reliable, smoother functioning mass produced price point rifle. 

[Mad Monk]

Going way back in time here.  I switched my Lyman GPR flint over to one of Bernie Tolino's mule ear locks.

[Wingshot]

The flash channels in the breech plug is tiny, I have opened them up to get reliable ignition.  The tang is oddly contoured and makes a strange hump back profile, I have altered that.  The trigger and lock parts are rough castings, I have finished them properly.  The result is a better looking, more reliable, smoother functioning mass produced price point rifle.

I’d be curious to read more about the flash channel mod. I’ve had, at times, ignition issues but found that painstakingly sizing and installing a good flint coupled with minimizing the amount of priming increased reliability. The one thing that’s always bugged me is that the flash hole liner protruded too far into the breech. I’ve thought about pulling the breech plug and dealing with that.

[Darkhorse]

Going back in time here too, so far I'm having a hard time remembering. First though a word about the powder chamber, this chamber is much smaller than the barrel ID and sometimes when you charge your rifle the powder bridges and none actually makes it into the powder chamber. So when I would charge my GPR I held the barrel at an angle and slowly poured in the powder all the while tapping the rifle with my palm. Plus a visual check that powder actually is present in the touch hole.
OK back to the GPR, First thing I did was draw up a better touchhole then I first modified some Lyman touchholes, then I made some on an NC lathe at work.
My stock swelled and impinged upon the sear and the gun didn't work anymore. Remember at this time I was a complete rookie and it took awhile to get it figured out. So I ordered a RPL trigger. And it didn't work either. Because the trigger assembly wasn't the problem in the first place. Finally it dawned on me what the problem was and a few scrapes with a 1/4" chisel got me shooting again.
So now I've got an extra trigger and I decided to improve the older one. This is where I learned to keep spare parts handy.
I also replaced the lock with a RPL and used the old lock to experiment on, my first foray into the mysteries of the flintlock.
I did some polishing of the new lock and surprisingly it made it better.
I replaced the sights but I can't remember what kind the rifle ended up with.
The rifle turned out to be a real shooter and the guy who bought it had lusted over it at a shoot one day after I let him shoot it a few times.
So I'm a tinker'er and that old GPR is what got me started on tuning locks and triggers.                                       

[OldMtnMan]

I mostly use a caplock. I had one GPR flint and the lock was terrible. Being a LH it wasn't easy finding a replacement lock. I sold it. Besides a half stock flint wasn't made back in the day. In my research anyway.

I always replace the trigger with a Davis. I just did that with my present LH Caplock .54.

I never have a miss/no fire by making sure the breech channel is clean and dry. When loading I always hit the barrel with the heel of my hand. First to get the powder down and then lean it over in the direction of the lock and hit it a couple of more times. I also use nothing but real black and always use RSW musket caps. Ignition is fast and reliable.

Match the wood to metal fit, refinish, and brown the metal. I use the primitive rear sight it comes with. Adjustable sight it also comes with is junk and not period correct.

That's about it. It's a good hunting gun but getting kind of heavy for my age. Although that makes recoil pleasant.

[Pukka Bundook]

A Lyman G-P (used) was my first percussion rifle. (.54) 30 -odd years ago.

I too altered and opened up the patent breech, rounding out the corners, worked on triggers and lock, and for looks, chopped that ugly hump down behind the breech.

It shot V well, with both 60 grs and 120 grs.  (hunting load the latter) 
It was a 1 ~48" twist as well.

[OldMtnMan]

A Lyman G-P (used) was my first percussion rifle. (.54) 30 -odd years ago.

I too altered and opened up the patent breech, rounding out the corners, worked on triggers and lock, and for looks, chopped that ugly hump down behind the breech.

It shot V well, with both 60 grs and 120 grs.  (hunting load the latter) 
It was a 1 ~48" twist as well.

I've never heard of that twist for a GPR. I know the older ones were 1-66 and they're now 1-60. Are you positive it was 1-48? The trade gun was 1-48.

[Hungry Horse]

A close friend has been shooting a Great Plains percussion for several years, and decided he liked it so much, that he wanted one in flint. His wife got him one for Christmas, what a piece of junk. As sent it wouldn’t fire because the frizzen was made out of junk. A replacement frizzen only helped marginally. Then they recalled the gun to replace the breech plug. The owner finally bought a replacement aftermarket lock which made it semi reliable. He could have bought a plain Jane custom gun for what he has tied up in this marginal rifle.
 I used to recommend the Great Plains to all novice shooters, but no more, they’re just another unreliable entry level muzzleloader now.

  Hungry Horse

[OldMtnMan]

Only the flints are bad. Show me a real half stock Hawken in flint? I could never find one, so I only use a caplock now. They work fine.

[Flint62Smoothie]

The Lyman Great Plains Hunter model has the 1:48” twist.

[Scota4570]

I was writing about cap locks. 

I never worked on a flint one.   I looked at one closely for a guy who was having lock trouble.  The lock was pretty sad,  sloppy fitting parts, the frizzen did not open properly, poor sparker.   If they are all like what I saw, I would avoid the flint version. 

Forgot to mention the stocks are some sort of mystery hardwood. 

They are a mass produced price point gun.  They can function OK but need work.     

[OldMtnMan]

The Lyman Great Plains Hunter model has the 1:48” twist.

1-32

[Daryl]

Taylor did a fairly complete rebuild on a GPR for our good friend Brian, in Smithers, BC.
I cannot find it.

[Wingshot]

My stock rifle is a flint, .50 cal and I too consistently bump the barrel to make sure the powder gets where it’s supposed to. Mine is a 1-66, 70grains of 2F on the range, 90 in the woods. I only use swagged round balls, .015 patching with bore butter. It’s always been easy to load and it’ll give you a distinctive “crack” as long as it’s not over charged. 100 grain and she booms and the accuracy suffers a little. My experience anyway. I’ll probably leave it as is since it’s served me well for so long. I’m gathering tools and parts to build my first longrifle.

[OldMtnMan]

My Lyman GPR was percussion. The only thing I did to make it competitive was to change the sights. The club that I shot at allowed any sight. So, I knew the sight upgrades I would use. I purchased a Lyman peep sight for the rear with an adjustable aperture. To fit it to the tang, I made a tapered adapter. Used screws and dowel pins to position. I used a globe front sight with interchangeable inserts. My shooting improved 100%. The Lyman Great Plaines Rifle is the best production rifle I have ever owned. I gave it to my son. He has it just the way it was the last time I shot it. Jerry

You should have bought the GPR version of that sight. It comes with the tapered block to go under the sight.

[Jerry]

Thanks Pete, At that time I didn’t know those sights were commercially available. Plus, I had access to some milling equipment. I did hold my own in those days, but much younger then. Thanks Pete...

[Shovelbuck]

They can be made to look more authentic but as for shooting, they are hard to beat. I had a .50 flintlock and it was just as reliable as anything I own, and I don't settle for sub par performance from a flinter. Only thing I changed on mine was to polish up the triggers. Some folks gripe about the flintlock version not being very good but that sure wasn't the case with mine! I gave mine to my son as he was wanting to get into flintlocks and I felt it was so reliable that he wouldn't get discouraged as many do that can't figure out or shoot a flinter. As for not being PC, to each his own. PC means personally correct for me!

[OldMtnMan]

They can be made to look more authentic but as for shooting, they are hard to beat. I had a .50 flintlock and it was just as reliable as anything I own, and I don't settle for sub par performance from a flinter. Only thing I changed on mine was to polish up the triggers. Some folks gripe about the flintlock version not being very good but that sure wasn't the case with mine! I gave mine to my son as he was wanting to get into flintlocks and I felt it was so reliable that he wouldn't get discouraged as many do that can't figure out or shoot a flinter. As for not being PC, to each his own. PC means personally correct for me!

You wouldn't have got mine shooting good. It was a LH version and they really screwed up making the lock. Even a white lightning vent liner wouldn't help it. It was reliable and always went bang but it was slow and nothing I could do or others either could speed it up.

You're right about the PC part but I have my own standards and those have to be met. I don't care what others think but when I look at my guns they have to satisfy me.

[Anonymous]

Put a L&R flintlock on a GPR kit from the get go.  Love it. Outshoots (faster and more consistent) than another GPR flintlock with factory lock that I have when shot head to head.  Only a statistically significant sample of one, but I am impressed with difference. Likely better options, but I am not aware of them. Downside, L&R lockplate does NOT match the factory lock mortise.  Over sized in some areas, undersized in other areas.  Not talking about internal cutout for springs and such, but actual lockplate shape.

[Pukka Bundook]

Mountain man Pete,

Yes, it was definitely a 1 in 48" twist.
I was told a good few times over the years that it wasn't, but I know how to test for twist and it certainly was.

I did the test numerous times, and it always came out at 1 in 48".
I did have a .50 cal one time, and it was 1 in 66".

Maybe I should have kept the old .54, if it was a rare one!

[OldMtnMan]

Did it say Great Plains Rifle on the barrel? It was 32"?

[Pukka Bundook]

Yes and Yes, Pete. Definitely nothing but a G-P.

I might have  a photo somewhere, but it was pre=digital, so would take a bit of finding now.

[OldMtnMan]

Well, that has to be a rare one. First time i've heard of it.

[Darkhorse]

This is a scan of the 1975 Lyman Blackpowder Handbook. You could order the GPR with a 1-60 twist for PRB's. Or a 1-48 twist for elongated projectiles. Yes Pete, a person could actually order his preference as I did.