tumbler question

[chuck-ia]

Pulled the hammer back to full cock, started to shoulder gun and the hammer fell, won't hold on full cock now. Took the lock out and watched the tumbler, sear as I pulled it back to full cock, sear slips out of tumbler notch. I took the lock apart and filed a little to change the angle on the tumbler, then I stoned the notch, it is pretty close now, seems to hold solid on full cock. This tumbler has only probably 200 shots on it, is it possible it is not hardened properly? After filing and stoning, do I need to reharden and temper? If I have to reharden can anyone give me some instructions? thanks, chuck

[Dan'l 1946]

What make of lock is it?

[erdillonjr]

Thats why I only buy chambers locks. They are gaurnteed. Ed

[chuck-ia]

The lock is a Chambers Late Ketland. I thought about sending it back again, but decided to save myself the postage, I guess the worst thing that can happen is I ruin a tumbler, which I think I will get a spare anyway. chuck

[Stophel]

It was probably always angled a bit wrong, it just waited a bit before it decided to start slipping off.

Was it easy to file, or did it file with a bit of resistance?  It should be fileable, but with at least a little difficulty.  If it filed really easily, it could well be too soft.

[Blacksmoke]

Chuck-ia,    Not to bad mouth commercial locks but they all need to be "fine tuned" to work properly. I've had to tune a number of Chamber's locks as well as Siler and others.   Part of the fine tuning is the proper angle and the surface on the nose of the sear.  This angle is critical to keep the sear engaged in the fullcock notch even without the sear spring being in place. The tension of the mainspring on the tumbler and the angle on the sear nose will force the sear to engage rather than to disengage. The smoothness of the bearing surfaces on both the sear and tumbler will aid in a smooth trigger pull.        Hope this helps,     Hugh

[chuck-ia]

It seemed to file somewhat easy. Right now after stoning, the trigger pull is about right, maybe a little on the light side, I do have the trigger pinned through the stock, as high as I could get it. I have never messed with the lock internals before, decided it was time. It is a bugger to get the right angle on the tumbler with my eyes, had my magnifiers on and that helped a lot but still hard to see. I think I will leave it as is and shoot it and see what happens, if I have to buy a new tumbler I guess that is not a big deal. Right now I have the same trigger play on half cock and full cock, (after filing the full cock notch) which I like, but not a big deal. thanks, chuck

[Don Getz]

Chuck.....If it were mine, I would return it to Jim Chambers.  When you think of all the locks that they sell, things like this
can happen, and I must say that with his locks this is very seldom.  I'm sure Jim would fix it for you, after all, he doesn't
want any of his locks out there that don't work.  It sounds like the tumbler might be soft, they should be pretty hard to file.  Send it back, he'll fix it................Don

[Ian Pratt]

  Unless there was a bad casting involved (which you'd rarely see on one of Jim's locks) I don't think you'd see a tumbler notch wear to the point of slipping after only 200 shots, even if you suspected it was improperly tempered. Something else to be considered, I have seen the problem you describe caused by a sear screw being over tightened and/or inadequately lubricated, the more times the lock is cycled the more it galls against the plate and bridle and eventually won't stay in the tumbler notch. Disassembling the lock to work on the tumbler then reassembling may have been what "fixed" that. Simple enough to check this, remove your internal springs. If your sear seizes up when you tighten the sear screw, it needs some attention. Don't need to bear down on the screw, just snug it up.   

[frogwalking]

You said the trigger is pinned high, through the stock I assume, not one pivoting on an extension of the trigger plate.  You may have checked this already, so forgive me if  you have, but  if the top of the trigger that bears on the sear is a hair too high, then disassembly of the rifle, say for cleaning, then reassembly with a slightly different tension on screws may have only just now made the situation visible.  That is the problem may not  have been in the lock but the trigger fit.  I only suggest this because I have done it.  It would be good as it is easy to fix. 

Of course, if the sear still won't hold when the lock is in  your hand, then this disproves my theory.   Good Luck.

[chuck-ia]

Thanks for all the suggestions. Sear would not stay in tumbler notch with lock in my hand. I did take the main spring out and the sear spring allso, sear moved with no binding as did the tumbler. I think I will e-mail Jim Chambers and see if he will have a look at it, I don't feel completley confident with my repair, I think the tumbler is not hardened correctly, (my repair will not last). I can be rather picky, but I spent about 400 hours making this rifle from a blank, and I want it right. thanks again, chuck

[Blacksmoke]

Chuck-ia,   Good choice- I 've known Jim Chambers for over 30 yrs. he will fix you up I am sure!  A malfunctioning lock is a potential "widow maker" and should always be fixed or replaced! We do not need another "statistic accident" on the firing line!    Hugh

[doug]

I think the tumbler is not hardened correctly, (my repair will not last). I

     You should not be able to file the tumbler at all.  It sounds as if the tumbler missed the hardening process.

cheers Doug

[Acer Saccharum]

A thing that really bugs me about store bought locks is that darn sear screw...when tightened down, it binds the sear. So many shooters have to fiddle withe the screw, and you know it's always moving.

So I like to take material off the bottom of the head of the screw so that the screw can actually tighten up without binding the sear. I suppose you could also run some soft solder on the last few threads to make a snug fit.

Best is to fit a new screw that shoulders on the plate. But not everyone has a lathe.

There, it's off my chest.


Chuckia, you tumbler is definitely soft from your description. You can reshape the notch, but it's just a matter of time before it rounds off again. Boom! ops, sorry, man, for that ball through your roof.

[T*O*F]

Best is to fit a new screw that shoulders on the plate. But not everyone has a lathe.  There, it's off my chest.

No lathe required........you can buy screw blanks from Brownells in all sizes.  You just thread them with a die.  The other thing that bothers me are lock and tang screws.  They are all overthreaded.  You build a gun and the guy that buys it thinks he's a gorilla every time he removes them for cleaning.  They compress the wood and pretty soon you've got lock or trigger problems, or an accident.  I use screw blanks for them and stop the threads so they can't continuously be overtightened.

[chuck-ia]

Good idea on the screw blanks. Actually, on this lock I can snug the sear screw down snug and it does not seem to bind at all, I do back it out about 1/4 turn out of habit though. I e-mailed Jim Chambers yesterday using the e-mail address on his web site, but haven't recieved a response yet. I decided not to shoot this gun till I am confident of the repair. I had this urge to shoot the 62 cal. smoothbore yesterday, which has a round faced english lock on it, fun time. I have 5 other guns with Chambers locks on them, this late ketland is the only one I have had troubles with. thanks, chuck

[bob in the woods]

I don't claim to be lock savy, but a couple years ago, I had a late Ketland lock which would not reliably hold full cock until I refit the fly. Took out the fly, it worked perfectly. put it in..wouldn't hold.  Carefull filing fixed it.

[chuck-ia]

I thought the fly might be the problem too, before I took it apart I watched it close, it would move freely, not touching the sear on full cock. thanks, chuck