Broken Tumbler

[Pete G.]

I have an "American Colonial" lock which has broken the half cock notch on the tumbler. It is fitted with a detent and used with a single trigger, so theoretically this should not happen, but nevertheless, stuff happens. I can cycle the lock slowly when it is out of the stock and everything seems to work properly i.e. the sear nose does not catch the edge of the notch. Perhaps the detent hung up some time, but I  can't really see any evidence of that (other than the broken notch).

What could I be missing here?

[mattdog]

First I'll take a chance that what you are calling a detent is the fly.  A lock with a fly shouldn't have this problen unless the fly isn't working correctly.  When cycled to full cock the fly should snap forward of the sear nose.  I would check to see if it is possible that the sear can go into full cock with the fly still behind it.  If it can do that then the fly is too small for the rebate in the tumbler or is simply too short to catch the sear when it gets past the full cock.  It can be an intermitant problem and not happen every time the lock is cycled but it only takes once for it to damage your tumbler.  It can be frustrating.

[Dave B]

It could be some one tried to pull the trigger while it was in half cock with enough force to crack it or break the notch out right. If the half cock notch is not damaged the nose of the sear can be damaged from this kind of treatment. I have had this very thing happen to one of my cap and ball pistols twice. It is very irritating to have happen with a new shooter.

[snowdragon]

When the hammer/cock is initially pulled back, the tumbler will engage in the halfcock notch with the fly to the rear (out of the way).  When the hammer is pulled to fullcock then tripped, the fly acts like a switching lever to cause the sear to ride over the halfcock notch.  What I suspect happened to your lock was that the hammer was pulled back into halfcock, then the hammer was hit very hard to shear off the halfcock notch. In other words, your gun was dropped right on the hammer .

The only reliable and safe way to fix the broken tumbler is to just replace it.  Good luck. Bill

[Bob Roller]

Detent,"fly"or intercepting cam.It's all the same thing.

Bob Roller

[Mark Elliott]

If you completely broke out your half cock notch,  I wouldn't expect the fly to keep the sear from hanging on what's left.   You are simply going to have to order a new tumbler.   Actually,  I keep a spare lock for my shooters for this very reason.   I sometimes get distracted at the line and try to fire the gun at half cock.  As all my shooters have double set triggers,  I occasionally break a half cock notch.   No problem though,  I take the tumbler out of the spare lock and replace it at my leisure.   It is very convenient that we have mass produced locks with mostly interchangeable parts.   If I hade to make a tumber each time, that would be a bummer.  Although,  I have made so many of those things,   it wouldn't take nearly the time it once did.   The secret is either use wrought iron or cobalt lathe tools

[Pete G.]

Actually the notch was only broken about halfway across, which is what was so perplexing. I once stupidly broke another notch by dry firing the set trigger after placing the hammer on half cock. I guess that I thought I was being safe; in reality I wasn't really thinking.
I believe that this problem probably occurred from grease holding the fly in the rear position. Theoretically it shouldn't matter with a single trigger, but maybe there was just enough contact as the notch passed the sear to cause an impact. The solution (for now) is to slightly bevel the leading edge on the replacement tumbler and to clean out any grease and use a touch of oil instead. Thank Goodness and Eli Whitney for interchangeable parts.

[TMerkley]

I have repaired an old tumbler from the 1870's using a triangular file to deepen the notch and then narrowing the metal infront of the notch to make sure that it fuctions' properly.  On another rifle I added a half-cock notch to a tumbler that did not have one before using the triangular file.  It's not hard, just takes about an hour sitting down at a desk or about 20 minutes at the vice. 

[Old Salt]

Actually the notch was only broken about halfway across, which is what was so perplexing.

I broke one in a similar fashion by trying to pry the cock off the tumbler instead of punching the tumbler out of the cock as it should be done.  The lock still worked but I wasn't comfortable with it so I repalced the tumbler.

At a later date I filed the half cock notch until the chipped section was gone and reinstaslled it in the orignal lock.  It still works today.