how to alter roundface lock sear depth

[ffffg]

i have a chambers round face flintlock that is perfect in every way except the sear knotch is very deep, giving a large amount of creep that has cost me some important shots.. i want to solder a brass block in the bottom of the sear to take out the creep ... i want to do it my self as whenever ive had anyone work on triggers for the last 5 years i get back a poor job in the name of "safty" or "liability"..(im talking about small local buisinesses,).. im very particular about this and want to do it my self.. the question is how do i take apart the lock? when i compress the mainspring it doesnt come out.. what is the dissasembly order to get the sear knotch part out... when i get it apart will 500 degree solder be ok to put a piece of brass in the bottom of the sear knotch? will it take any of the temper out of this next to perfect lock that i enjoy very much?? thanks dave..

 

[Roy]

Do not apply heat to the tumbler it will make it soft. You can stone the full cock notch a bit to make it more shallow and stone the nose of the sear a bit, but if you have never done this or have seen it done it can be a good way into having to buying new parts.

Do you have a mainspring vise?

 

[rich pierce]

Take the cock to full, put on mainspring vise, release the sear and allow the cock to go all the way forward, and the spring should come out with some jiggling.
Loosen the screw for the sear spring a lot and pivot the spring up out of the notch in the plate ans weing it out of the way. Remove the bridle and sear.
Loosen the screw holding the cock on the shaft and rap it with a brass or plastic faced hammer. This should loosen the cock from the tubler. Remove that screw and take the cock off the tumbler. Now you have the tumbler in hand. Do not lose the fly! Tape it to the face of the lock NOW (experience talking).

I would stone the body of the tumbler at the full cock notch but this must be done squarely and you must not alter the angle of engagent at all- don't fool with the notch a bit, just lessen the depth by removing steel from the circumference of the body. Others solder a piece in there but that alters the hardness and I don't like that.

 

[paulvallandigham]

The upper arm of the spring ends in a short wedge, that fits into a groove in the bottom of the bolster. To remove the mainspring, you have to not only clamp it when it is in full cock mode, but then pull it with a twisting motion to get that wedge out of the groove. There is also a small flange, "tab", or " pin" near the bottom of the V that fits into a hole in the inside of the lock plate that helps hold the lock in place. Those two points, and then the claw or hook that makes contact with the tumbler are the three points that hold the mainspring in place. Always let the cock do the compressing of the spring. If you try to compress the spring with your pliers or spring vise, you can overdo it, and possibly harm the spring. If you have vise grips, you can tape the jaws to protect the surface of the spring, and then simply set it so that you can close the visegrip on the compressed spring. Release the sear to put the spring under tension in your visegrip, and the rock it out from under the bolster. Set it aside. Obviously, if you have use for visegrips, you want to have a second set of them, as you want to lease the spring compressed and in the visegrips as they are. Once the mainspring is removed, a screwdriver will remove the bridle, and then the tumbler. You will also need to remove the trigger return spring, and the sear bar, but again, a screw driver works here, too. I put a clean white town down and set the parts of the lock I am not working on in a logical sequence on the towel to aid me in reassembly. The screw for the trigger return spring stays with theat spring, etc.

 

[Stophel]

How far away from the sear "bar" is the trigger pivot pin? If it is less than a half an inch, it is too close, and that could easily be the culprit.

(the closer the trigger pin is to the sear, the lighter the pull will be, but it will also be longer. The farther away it is, the shorter the pull, but it will be slightly heavier. Since the weight of the pull can be adjusted elsewhere, I have found 1/2 inch to be the ideal distance. Once, long ago, I did one where the pin was 3/8" from the sear. The pull was very light, but INCREDIBLY long. I never did that again!)

 

[LRB]

DO NOT stone the tumbler down to lessen engagement. You can get into all kinds of trouble if you go to far.You can solder a small piece of steel just behind the tumbler notch which becomes a regulator for the sear engagement. The sear will set on this piece, and then you file the added piece down to allow whatever engagement you want. If you apply heat from under and behind the notch, it will have no effect on the temper.Use a low temp solder that flows around 430o, and don't get carried away with the torch. If you have no experience with soldering, no problem. Use J&B Weld to make small mound behind the notch, and file it to do the job. NEVER file down a tumbler, or other similar system to get less engagement. That can cause more problems than you started with. If you go with the J&B, be sure to rough the surface and get it very, very clean for a good bond. You pay the shipping both ways, and I'll do for you if you like. Send just the lock.

 

[Stophel]

When you file/stone down the tumbler, it messes with the clearance of the sear nose/half cock notch, and the action of the fly.

If the notch is still too deep (which, without seeing it, I find unlikely) even after checking the trigger pin position and finding it to be correct, you can do something like this: On one lock set I got from the Rifle shoppe, the full cock notch was REALLY deep...much deeper than the thickness of the nose of the sear (having the notch the same depth as the thickness of the sear nose would be, in my opinion, the ideal). I hated to have to do this, but I did it and it works. Drill and tap a hole just behind the full cock ledge into the body of the tumbler, and install a small screw. Sink it down tight, and file the head off until the sear makes the amount of engagement that you want. The screw can then be hardened and tempered along with the tumbler, or taken out when hardening the tumbler. Locktite that sucker in so it won't move.

Any work like this that you do to the tumbler will require annealing it down first, and then rehardening and tempering it.

 

[rich pierce]

OK guys I'll not disagree with your advice that one should not stone down the body of the tumbler- but I could show you how it works when done right! :rotf:

 

[Roy]

I guess we all have different ways of doing things :v

 

Dave, somethinmg to consider, or at least be aware of, is that, if the tumbler was designed correctly (being a Chambers it likely is), the half cock and full cock notches as well as the lower sweep of the tumbler (where the scear rests when the lock is uncocked) will be all on the same circular plane. This means that the scear bar will be in the same position with the cock at rest, in half cock and full cock. This is so the trigger can be installed with just a few thou clearance and will not be pressing on the scear or sloppy in any position. If you shim the full cock notch you will move this position out of the circular plane and at full cock the trigger will be sloppy. Just something to keep in mind.

Cody

 

[ffffg]

i dont know the terms, but the nose of the sear end is narrower than the notch on full cock.. the knotch is about 1 1/3 times the nose (of the sear) depth.. the trigger pin is close to the sear bar, probably about 3/8 inch or slightly closer.. i cant feel the creep on the lock itself when its off the gun, it needs to be mounted in the gun, then the pull feels like a mile long.. i often pull the trigger, then relax and pull it again during a shot.. fine when the target isnt about to run away!!! from the description youve given on dissasembly ill never get the darn thing apart,.. so i think ill call jim tommorow and send it to him... if he wont fix it ill have to send it someone who will do it the way i want... thanks dave..

 

It's a Chambers lock-IT'S GUARANTEED- first give Jim a call, and see what he says, he'll probably tell ya to send it to him and he'll fix it. I know some of you are excellent locksmiths, but Jim is a master, and it's his problem to fix, if it has a problem. It may not even be a lock problem, it could be trigger to lock geometry issue. I'm not trying to be pissy here, but why not just tell people to get it fixed under warrenty, and then let them tell us how good or bad the service was. Stoning or shiming a tumbler without the proper knowledge, and it's new tumbler time,no lock maker should be stuck replacing one, when it's not necessary. Just my two cents Bill

 

[Roy]

could be that this is what I read.

i want to do it my self as whenever ive had anyone work on triggers for the last 5 years i get back a poor job in the name of "safty" or "liability"..(im talking about small local buisinesses,).. im very particular about this and want to do it my self..

But you are right send it back to Jim. :v

 

[LRB]

Cody, you are correct about slop in the trigger, but that has never bothered me as usually it is not that much. Rich, I have no doubt that you can reshape a tumbler correctly, but this guy cannot even take a lock apart yet. I should have been more explicit in my post, as my advice was in regard to amateurs, which certainly does not include you. I know your reputation for being a fine smith. Sorry, if you took offense, but I still stand by my post as being the simplist way to get a good trigger without mucking anything up, and I doubt that Jim Chambers would correct it, due to legal liability issues.

 

[John Taylor]

Sounds like you would be better off with a set trigger and not mess with the lock. If you don't feel creep in the lock but feel it when the lock is on the gun then the trigger pivot point may not be in a good location. It also helps if the trigger is polished where it comes into contact with the sear bar. Any roughness in the contact area will cause a rough trigger pull. Changing the pivot point on the trigger will change the length of pull, as the pull get shorter it will also add pounds to the pull. All this assumes that the lock is top quality. When I build a lock I sometimes put a screw in to adjust sear ingagement.

 

[rich pierce]

Rich, I have no doubt that you can reshape a tumbler correctly, but this guy cannot even take a lock apart yet. I should have been more explicit in my post, as my advice was in regard to amateurs, which certainly does not include you. I know your reputation for being a fine smith. Sorry, if you took offense, but I still stand by my post as being the simplist way to get a good trigger without mucking anything up, and I doubt that Jim Chambers would correct it, due to legal liability issues.

Wick, your advice was well-given and intended and no offense taken. This forum is for the exchange of ideas. I think we probably all agree, now that we know the trigger pivot is so close to the sear bar, that the real problem is one of leverage and he's going to have creep regardless of lock tuning measures. I'd say about 75% sure that moving the trigger pivot forward 1/8" or even 3/16" would change the feel completely. Plus the lock would remain a very safe lock. I used to have a .22 when I was a kid that was unsafe- the sear was a stamping and not hardened right- and it's a miracle nobody ever got hurt with that gun. So safety first!

 

[DrTimboone]

Having installed a Stan Hollenbaugh set trigger in my very slim So Colonial with a Chambers English lock I think I exhausted all of the advice I could get to get the trigger and lock to work properly in a stock that did not offer much room for forgiveness. The geometry of the trigger pivot and sear angle to the trigger bar are the issue is my bet. I got advice from Stan and Jim and did everything they suggested to the trigger and the lock and then got advice from someone else about the distance between the pivot and the sear and that solved the problem. No creep and light pull!! It is a complex geometric system and the locks being well made, it comes down to pivot point and height of trigger bar to get the system optimized.

I wouldn't mess with the lock. But give Jim a go. He will be helpful!!

my $.02 worth

 

[Stophel]

3/8" from pin to sear?...I knew it! :winking: