GPR half cock

[J. David]

I have not shot my GPR for a long time, is it supposed to have a half cock? if so I guess it's broken.

 

[Beaverman2]

When was the last time you cleaned and oiled the lock?

 

[J. David]

Probably 4 years ago. Last time I shot it.

 

[akroguy]

Remove, inspect, oil the lock. Reinstall without over-tightening the lock bolt.

 

[Trot]

The Investarm locks do have a halfcock, but it is really low, not really enough room to cap it with it on halfcock.

 

[J. David]

Well I just remembered or discovered one problem. I had been using musket nipples. I put the standard nipple back in and it half cocks. It is really close to the nipple. Is that normal? also the hammer will drop when the trigger is pulled at half cock. It looks like the half cock notch is not deep enough. I remember when I got this back from my father in law the triggers were awful and I did some work. They do work nice and smooth but I am not sure what's up with the half cock.

 

[Phil Coffins]

This is what the lock looks like, you may have a broken sear.
A8C9B4BF-FBC6-4B36-AF9D-7BE2994DC852 by Oliver Sudden, on Flickr

 

[J. David]

Yea, it don't look like that.

 

[J. David]

Top picture is full cock and bottom pic is the half cock. I remember now that when I assembled the rifle 20 years ago it would catch on the half cock when firing, perhaps I removed too much material. Do you think a new tumbler will fix it or should I get a sear also?

 

[Grenadier1758]

@J. David, you probably need a new sear, fly and tumbler.

When a double set trigger catches the half cock notch on firing, there is something wrong with the fly or the sear nose. Removing material from the tumbler won't fix that issue.

I don't see the fly in your picture with the lock at full cock and the half cock notch doesn't have enough of a notch to hold the sear in the half cock position.

 

[Phil Coffins]

Yes, your tumbler is broken and there is no fly.

 

[J. David]

Parts from Lyman or log Cabin Shop?

 

[SDSmlf]

View attachment 378667View attachment 378668
Top picture is full cock and bottom pic is the half cock. I remember now that when I assembled the rifle 20 years ago it would catch on the half cock when firing, perhaps I removed too much material. Do you think a new tumbler will fix it or should I get a sear also?

You appear to have lost the fly and given the half cock notch on the tumbler quite the hair cut. Can’t tell what you did to the sear, but agree with @Grenadier1758, you need a tumbler, fly and sear.

Below are photographs of an unused Lyman/Investarm lock at half cock and full cock. Note the fly and the positions in both photographs. Also note the depth of the half cock notch.

 

[J. David]

You guys are awesome. Thanks. I must have lost the fly right off the bat, The gun would hang up on the half cock when fired. I remember removing a lot of material from the tumbler. I then switched to musket caps and never really thought of it until today. I found the original nipple and I have thousands of #11 caps and I noticed when the trigger was touched at half cock the hammer would drop. I have been shooting flintlocks for the last 15 years or so pretty exclusively and the poor GPR has been in the safe. Got a hankering to shoot it all of a sudden. Must be all the talk of the Kibler Hawken coming out. Anyway I just ordered the parts and will get in safe working order.

 

[Indy Durtdigger]

Am I the only one seeing cracks on the plate going up to and around the tumbler pivot? Looks like rust and some stock contact but blow it up and take a closer look.