Sear catching at half-cock

[Bob Gerard]

Hi Guys,
I have had this "Murdoch" flintlock pistol for 30+ years and it's always sparked and fired well,  (bought from Dixie Gun Works).
Last week I cleaned it up a little including the inside of the lock, just with some light oil and a toothbrush. I didn't dis-assemble it at all.
I replaced the lock and now when I go to pull the trigger, the hammer stops at the half-cock notch.
(It has no fly). The trigger bar is a simple lever type with no spring.
I am wondering why. The sear spring didn't move or get stronger. The parts haven't moved at all. I am wondering if I could slightly grind down the half-cock notch on the tumbler surface so it wont catch? It looks like the notch is beveled correctly so it cant slip out of half-cock even with some ground off the tumbler.
I attached a picture of the lock's guts.
Thanks.

[Bob Roller]

The full cock position looks way too shallow and I think the years of shooting have created a very light trigger release that will not allow the sear to get past half cock.The half cocked position also looks a bit shallow as well and ought to be recut enough to firmly engage the end of the sear.
Bob Roller

[Bob Gerard]

Thank you Rob, I appreciate your help.
I am wondering of I remove some metal off the tumbler at the half-cock it will work.
Here is a picture of what I was considering.
Also, would lightening the sear spring help?

[rich pierce]

Firming up the pressure it takes to release from full cock will cause the sear to stay up momentarily while firing and miss the half cock notch. I think that’s the same as Bob indicated. Very light trigger pulls on locks with no fly result in the situation you have - sticking in the half cock notch. A better engagement on full cock will help.

I’d also polish all bearing surfaces to get as much performance as possible since you’re working on it.

[Bob Roller]

That's exactly the same thing and I am amazed at the durability of that particular lock.
Bob Roller

[Bob Gerard]

Thank you Rich and Rob! So the trick would be to deepen the full-cockk notch if I understand correctly?
Funny thing is that it worked just great until I cleaned the lock a few days ago (not un-assembling it but just using a brush and light oil). Goes to show how I can mess-up things 

[smylee grouch]

Would the bridle screw be too tight causing the tumbler to be not as fast as i9t was before? 

[Bob Roller]

IF POSSIBLE,reangle the full cock notch slightly so to make the trigger pull a bit heavier,The release will be a break and will probably allow passage past the half cock as the tumbler rotates.A Barrette file from a good quality set of needle files is my choice for this slight alteration.
The shape of this file is a wide triangle that cuts only with the flat side,
Bob Roller

[Bob Gerard]

Thank you Rob. Your advice is really appreciated. It might be beyond my skill set to attempt that fix and I may let someone else handle it. It has served me well.

[smylee grouch]

It seems strange that it worked fine before disassembly but not work after reassembly. Wood swell or too tight of side plate screws.

[Bob Gerard]

It's an all-metal stock (Scottish Murdoch). It appears the issue is the tumbler notches. Thanks.

[rich pierce]

It seems strange that it worked fine before disassembly but not work after reassembly. Wood swell or too tight of side plate screws.

If it was originally gummy or tumbler screws were down too tight this could increase pull weight enough to keep the sear out of the half-cock notch when firing. Anything that lessens friction results in a lighter pull with a simple trigger with a tumbler with no fly and so the sear tip is not held up when firing.

[Darkhorse]

I had one of my locks (large siler) do almost the same thing recently. I used the process Rich and Bob described to fix my problem. For some reason I had to resize the fly before the sear would pass over it. When you deepen the full cock notch be sure to cut it deeper at the rear of the (or front) of the notch. The area you have marked in red is where you will file a little off to gain clearance.
Personally I like to keep a fly in both my triggers, those controlled by set triggers and the single trigger also.
FWIW I never did figure out why my lock got out of rythem like that.

[Bob Roller]

The change in the radius shown in the red pencil line will work and deepen the half cocked position enough to hold against the thrust of the mainspring.That is the ONLY thing the half cock is supposed to do and none of them will stand to extreme pulls by someone trying to
see if it works.The sear or tumbler or maybe both will be damaged and then finding someone to repair it can be a problem.In 1980 I did make a new tumbler for a "4 pin"Brazier lock on a Whitworth long range rifle that belonged to the German team captain and we both thought it was deliberate damage by someone who didn't want to  compete against this high scoring German.This happened at Quantico Va,at an International match
and I think 22 countries had teams there that year.
Good luck with the repair and keep us posted.
Bob Roller

[geb324]

If it worked before I would not do any metal removal clean it again there is dirt some where you cant see.

[D. Taylor Sapergia]

This likely has nothing to do with the issue you are having, but I do see a mechanical issue I'd like to address.  The tip of your sear spring is bearing on the sear considerably back from the screw.  In my opinion, it should be bearing on the sear directly behind the boss for the screw.  It looks like the spring is rotated counterclockwise a little, pulling the lower arm's tip rearward.  This will increase the amount of pressure required to fire the lock, without serving any advantageous purpose.
If the spring has pulled out of it's notch in the plate, this can happen.  So check the sear spring's screw for tension, and make sure the inside tit is resting in the grove in the plate.

[Scota4570]

Question??  Why do some locks have the half cock notch further from the rotating axis of the tumbler than the full cock notch? 

That causes the OP's kind of problems.  The sear will bash in to the half cock notch.  When they make it like that, a fly is necessary even with a simple trigger.   I see no good reason to do that.  Is it about eliminating trigger slack at full cock? 

What am I missing?

[Bob Gerard]

Thanks everyone for your knowledge and suggestions on this. I have had the pistol over 30 years with great enjoyment in using it. I felt unqualified to make the repair and want this great little pistol to be enjoyed, si I decided to sell it to a gun builder who can get it going again. I have several other pistols to keep me busy for the duration so I feel happy it will be getting a fresh start in another’s collection.
Again, many thanks,
Bob

[Dphariss]

Question??  Why do some locks have the half cock notch further from the rotating axis of the tumbler than the full cock notch? 

That causes the OP's kind of problems.  The sear will bash in to the half cock notch.  When they make it like that, a fly is necessary even with a simple trigger.   I see no good reason to do that.  Is it about eliminating trigger slack at full cock? 

What am I missing?

Because some of the stuff being sold is not made by people who understand how a lock is supposed to work. They make them to sell and apparently don’t much care if it works or not. Some can, and have, take a good 18thc design and slop it up till it takes hours and a welder to make it work. There ARE good lock makers out there. But I am not naming any names on way or another. I just did 2-3 hours on one of our Guild members locks and it STILL needs more. But at least he and get the rifle finished and check set trigger function etc  then bring it back for a bushing of the sear. He ran out of time the other day. Then the poor guy at the range with a finished rifle that would not work. Apparently the guy that stocked it had no more idea how a lock (same lock BTW) is supposed to be and did not fix it.

[Bob Roller]

Lock MAKING is a skill set in itself and incorporated first is the interest in and the desire to see if such a mechanism is possible using present skills and tools.If possible,study the work of past masters of the trade.In my opinion,that means the lock filers of England.A few years ago on another forum I got the definite impression that the fine locks of the past ARE reproduceable but at a cost that is stunning.As the percussion era replaced the flintlocks,the mechanisms became more sophisticated and fine workmanship was directed to function more so than is non functional filing labor.The 3-4 and even five "pin"locks were carried into the cartridge era and are labor intensive to do but there is nothing non functional about them.The advent of machines such as lathes opened a need for precise measurements and the micrometer became the ideal way to measure once accepted standards were established.My tool kit is comprehensive and a variety of fine measuring tools are close by and when I worked in other shops,the general rule was that the man that had the most and best tools usually got the work.
Bob Roller

[Scotmur]

This lock looks like a gun I missed out on from another sight recently from a gentleman called pathfinder !! Would it happen to be the same one from a Murdoch I'm curious what the outcome is about the lock catching on halfcock Looks identical  !!

[Bob Gerard]

Hi Scott-  yes thats the same Murdoch pistol. (I am Pathfinder NC in the other forum).

[Scotmur]

Aw  ok . Well hello Pathfinder . I was searching and browsing other forums about a Murdoch and came across these pics of a lock that matched your pics to a tee ( I recognized the powder burn patterns ) !! So I assuming you still have it . Are you planning on trying to correct the problem yourself ?  Is it still available maybe ??

[RAT]

Here's a completely different suggestion based on the following personal experience...

I built a rifle and everything worked fine. When I took it to the range the first time I had a couple of failures where the cock wouldn't fully open the frizzen. The cock was stopped because the sear was catching the edge of the half cock notch. I also thought it was the fly. All it really was is that when I tightened the lock bolt too tight the wood inside the lock mortise was rubbing the fly and slowing it down through drag. I removed a little wood and the problem was solved.

[ettoreR]

I would disassemble and polish all bearing surfaces, and then see to take a small amount of metal off the half cock notch like you're thinking, just a few licks at a time. What I'd also recommend is put some blacking on the sear and tumbler, reinstall the lock, and work it a few times to see if your mortise has any protrusions that are causing/ assisting the hangup as well. Some playing around will fix your issue !