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ebiggs1

69 Cal.
Joined
Apr 27, 2009
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Since this is my first Lyman GPR, I have noticed it’s lock is almost an exact copy of a Thompson Center lock. Anyway the cock looks like one of the older TC cocks. The question is, is there an updated cock for the Lyman?
My GPR sparks well. It did so from the get go, even with the sawn flint. The flint strikes
about ½ way up on the frizzen. On my TCs the flint strikes about 2/3rd of the way up on the frizzen. Is this normal?
 
L&R makes 'drop in' replacements for many of the 'entry grade' rifles, including CVA, T/C and Lyman/Investarms. They call them the 'RPL' line: L&R RPL Locks
 
Lyman GPR, I have noticed it’s lock is almost an exact copy of a Thompson Center....
I'm thinking that that should read "the T/C lock is almost an exact copy of the Lyman.
I do believe that Lyman got there first.
Pete
 
Ha! I have to correct myself. T/C got there first. Their Hawken dates from 1970. The GPR started in 1980.
So....kinda ignore that other post, willya?
Pete
 
i changed the lock on my GPR to a L&R lock, keep in mind its not a drop in, you will be removing wood for the internal working parts of the lock. the instructions that come with it will aide in this as well as removing wood in the fence area. its not a major project just take your time. the difference between the 2 locks is night and day. The L&R lock is a heavier built lock with a fully hardened frizzen. Mine works beautifully. you have a good shooting rifle and the lock will only improve it.
 
Here is a pic of both.

IMG_3874.jpg
 
Good morning
Why do you want to change a lock that works ?
If you do not like the fake colors dopper it well with Rust remover and it will be white. Leave it unoiled in a humid area and it will rust or you could just Brown it.
But if it sparks realibly shoot it till it breaks.
I still like to opperate on the old farm thinking.. If it ain´t broke don´t fix it.
 
Good morning to you also,
That is a good question. My older style TC lock worked well but the new cock and frizzen work much better. They said the old style TC frizzen would wear out quickly. The Lyman looks like an old style TC cock. The Lyman’s flint strikes lower on the frizzen than I think it should but yes so far it has sparked well. Just little tweaks needed to be done.
 
I think the one in the picture is a 3/4x7/8 but I have 3/4x3/4 on hand. I can't go outside because it is snowing and sleeting again but I have been sparking the gun trying different things inside. I just can't seem to figure what is going on with it. It looks like the flint is striking the frizzen too directly instead of at an angle. But when I compare it to the TC lock, it seem almost identical and the TC lock works perfectly???
 
What I have determined to work best for my Lyman is. A bevel down flint and a rather full pan of prime. The touchhole drilled out with a #50 drill bit. I, now, think there are fewer sparks coming from the frizzen and the full pan is a better target for those fewer sparks. The fuller pan also makes a bigger fire to set off the main charge. I also think the touch hole liner needs to be replaced with a RNC.
 
Its been awhile since i shot my GPR But i think i went to a 7/8x3/4 flint and turned it bevel down to get it to hit higher on the frizzen. It might be worth a try.I agree the lock or at least the notch in the cock/hammer is similar to the old T/C cock. The older Investarms guns are of very close in looks and feel to the T/Cs. I own a few of each. You just can't beat the T/C warranty IMOP :thumbsup:
 
I agree with the almost full pan It seems to work better . I tried everything 1/3,1/2 full,away from the hole ,banked against the hole. I ended up with a drilled out liner & 3/4ish full pan of GoexFFFFg and R. P. flints. Things changed for the better after all of that. Mine also likes a load of 100grns of Goex FFFg in the bore & a .530 Hornady RB wih Oxyoke patching material cut at the muzzle.
 
What I have determined to work best for my Lyman is. A bevel down flint and a rather full pan of prime. The touchhole drilled out with a #50 drill bit. I, now, think there are fewer sparks coming from the frizzen and the full pan is a better target for those fewer sparks. The fuller pan also makes a bigger fire to set off the main charge. I also think the touch hole liner needs to be replaced with a RMC.”


Look at the oblivious difference between the touchhole liner of the TC Hawken and the Lyman. The TC is on the right in each pic. Why is the Lyman’s so much longer? Look at the backside and you can see the hole is much larger on the TC.
This is probably why the Lyman needs a bigger fire to set it off. Hope the RMC liner fixes this problem. Now I need to figure out why I and not getting the same amount of spark that I get with the Thompson Center lock. I see no reason why it shouldn’t spark equally as well.

IMG_3888.jpg


IMG_3889.jpg


IMG_3890.jpg

Lyman on the left. Thompson Center on the right.
 
I messed around with this silly thing a lot yesterday. I probably sparked it 50 times before I came up with this solution. The cock is too short. It is too short by about 1/8th inch. I put a lead wrap, which I typically don’t like, around the flint but I also put thick leather underneath. It helped the angle and has put the flint in a more advantageous place. It is very cold here so I won’t shoot it today but I am getting good sparks, a lot of sparks!

IMG_1231.jpg


IMG_1233.jpg


Now just get the touchhole fixed and ”¦”¦”¦”¦..
 
It's fascinating to watch and to read about this project as it has developed.
I keep telling my self that I should go and check the different elements of my GPR just to see how they match up. Interestingly, though, for me is the fact that I have just bought a new .50 cal barrel for my GPR. I wonder if it will work as well as the old one with the same lock.
As it is right now, I have Tom Fuller flints in bevel down and use about 1/3 to 1/2 a pan of FFFFg to prime. It always goes off (well....lets say it's very rare that it does not fire.)
I'd like to check the size of the touch hole - I'm a least the third owner of this gun; maybe some one else drilled it out. We'll see.
Pete
 
After I drilled my vent liner to 5/64th" and coned it, I relieved some metal from the inside with a drill bit from the back side. I measured the barrel thickness where the vent liner threads into and trimmed the liner to that length. These two actions allow more powder to reach the touch hole. Works for me :thumbsup:
 
This is what I just did. I drilled the front side out with a 5/64th drill bit. I coned it slightly wita a counter sink bit. I drilled the inside out with a 9/64th to slightly cone it, also. I don't see where shortening the liner will help but I agree it is too long. It appears like the threads go at least as deep as the liner is long. The barrel thickness plus the breech plug walls.
 

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