Tour of a Fine English Lock

[Stophel]

In order to make the much-vaunted one-position-sear, that full cock notch must be VERY deep.  It looks that way in the photo.  How would this very long let-off be countered?  Or would it?  The trigger pin would have to be spaced fairly far away from the sear bar ...farther than the sear bar is from the sear screw in order to "outrun" the sear lever/arm and speed that sear nose up as much as possible so that the trigger pull wouldn't take four minutes to let-off.  Am I thinking correctly on the mechanics of it?

Chris,

You are absolutely correct.  Having a very deep full cock notch isn't a good thing.  A fly solves the problem. 

Jim

Jim

That's the only two ways I can see to do it.  Either use a fly to bump the sear up (actually, down) over the half cock hook, or make the full cock notch and the half cock hook about the same radius away from center... and then you have to make the full cock notch at least as deep as the thickness of the sear nose, PLUS the thickness of the half cock hook to get the sear to sit in the same position at half and full.  I'm just having a hard time understanding how this ultra deep notch would be made to work satisfactorily.  That makes for a LOOOONG pull, which, I suppose could be compensated for by a really long, far forward trigger spacing, to attempt to speed up the sear nose.  I'm not sure how successful that might really be.  Maybe it's just a shotgun thing.  Follow through, and all that.  Just keep pulling the trigger until it goes off.  I'm definitely not a shotgun shooter.

 

[smart dog]

Hi Chris,
What are you talking about?  There is no "ultra deep" full cock notch on this lock.  The lip is just a little further from the tumbler spindle than the lip of the half cock notch.  It is not a "deep notch".  The trigger pull is light and crisp. I produce locks without flies that have light (1.5 lbs) and crisp trigger pulls all the time. You just have to have experience with that design and know what you are doing.  Actually having direct experience with these kinds of locks helps to understand them.

dave

[Stophel]

Forgive me, I'm apparently missing something entirely.

[B.Barker]

Wow what a great lock. I wish we could get locks this nice today but like Jim said most people don't understand a great lock. Most people refuse to pay for that kind of work because of the lack of understanding. I have to admit I was in that crowd at one time. Thanks for showing all of us the lock. I do have one question though. Does the lock "jump" a bit when fired or does it lay smooth in your hand. Not sure if that question makes sense or not.

[Stophel]

Wow what a great lock. I wish we could get locks this nice today but like Jim said most people don't understand a great lock. Most people refuse to pay for that kind of work because of the lack of understanding. I have to admit I was in that crowd at one time. Thanks for showing all of us the lock. I do have one question though. Does the lock "jump" a bit when fired or does it lay smooth in your hand. Not sure if that question makes sense or not.

You also have to realize that this was definitely NOT your average common-or-garden-variety gun lock of 230 years ago.  The vast majority of locks were nowhere near as finely fitted or finished.  This was a lock made for a gun made for an English gentleman, who had money to burn (or was highly in debt, but still felt the need to keep up appearances...).   

[flatsguide]

Dave, thank you for the photos and explanation of lock works. It was a small community of gunmakers and apparently they were all familiar with each others work. A question about triggers, were there any trigger springs that kept the trigger in contact with the sear that prevented a loose and floppy trigger?

Single triggers with no set capability can be lightly uploaded with a small spring and
this is standard on high end English percussion target rifles. The spring allows the
release bar to  follow the sear in all positions.
Bob Roller

Bob, thank you, that is nice to know. I appreciate your sharing your insights, especially locks and triggers.
Cheers Richard

[scottmc]

Smart dog, I'm going to ask a question but please dont execute me for the comparison 🤣 but the outside of the Mortimer is very similar to the l&r Durrs Egg (dont shoot) so was he influential in inspiring that particular lock maker?

[smart dog]

Hi Scott,
No.  It was a pretty commonly used style.  Durs Egg emigrated from Switzerland or France to London as a fully trained gunsmith  in 1772.  He came to work for John Twigg stayed with Twigg until he set up on his own in 1776.  In fact, he took over Twigg's premises in the Strand when Twigg moved his business to Piccadilly. You can make an L&R Durs Egg lock into something approaching this quality but it takes some working it over. 

dave

[Bob Roller]

The last two locks I made were the Durs Egg and they both had better looking mechannisms
and closer fit parts.It takes experience to do this and that is one thing I have and now hand
skills are being replaced by CNC and that is the order of progression and I am glad to see it.
Bob Roller

[Jim Kibler]

Dave,

Chris is right.  I don't think you are understanding things correctly.

Here is what you said in your original post:
The position of the sear does not change when the lock is at rest, half cock, and full cock as shown below.
That is highly desirable when you are fitting a simple trigger to the lock.  You can fit it so there is no trigger rattle at any position, and no trigger creep when firing.  The tumbler does not have a fly detent and doesn't need it because the gun is fitted with a simple trigger.  The configuration of the notches is perfect. As you can see the lip of the half cock notch is a shorter distance from the tumble axel than the lip on the full cock notch.

The key phrase is "the lip of the half cock notch is a shorter distance from the tumbler axel than the lip on the full cock notch"

With a one position sear, it would be required that the full cock notch be extremely deep for this statement to be true.   No debate, simple geometry.

Jim

[Dphariss]

The lock was probably made by a lock maker.
This should take you to scans of the "On Locks" chapter of W. Greener's  "The Gun" 1835
This book is available as a PDF on the WWW. Once you sort through the versions of "The Gun and It's Development"  by his son W. W. Greener

https://www.facebook.com/media/set/?vanity=100000127103372&set=a.4561092173904974

[Pukka Bundook]

Dave,
Not had much forum time  for a while.
Thank you for this thread.
Thank you also for your detailed study of the lock.   I must say, you See  very well!
I also greatly  enjoyed your writing of some of the English makers, including the progeny if you will, of Edward Newton.  He was a master craftsman even if a Provincial maker.   Elston of Doncaster was another.   

Thank you again for this detailed look!

Best,
Richard.

[jerrywh]

I think Dphariss is probably correct. This lock and most likely all the locks for the major gun producers in England were made by professional lock makers. This was an industry in England in the 18th Century and also most likely several people were involved in the manufacturer of one lock. Seldom was a lock ever made by one man. Different records testify that about 22 people were involved in the making of a gun in England. The Manton factory took up about a city block and was a 2 story building. I read someplace that he had about 250 employees.

[smart dog]

Hi and thanks for looking and commenting, everyone!
 I kind of put this thread on hold for a bit because I had to do other things and I wanted to add some photos and measurements of original locks to address the comments above by Jim Kibler and Stophel.  I will get that done soon.  Don, Richard, and Jerry are absolutely correct about multiple tradesmen involved.  Mortimer had a lock maker.  Some had them made "in house" and others subcontracted out.  My purpose was not to highlight the manufacturing process but to point out the features that make the lock so good regardless of who made it.  The Mortimer lock has a stirrup tumbler but a measure of that mechanical advantage and good geometry can be duplicated with a simple hook and toe tumbler.  The secret is to design the mainspring so the hook rides the full length of the toe on the tumbler ending up at full cock right against the axis of the tumbler. If you get it just right, the tumbler toe lifts the spring a little as you bring it to full cock but it also pivots around the end of the hook. The result is a little let off of pressure making it easier to adjust a light trigger pull with a simple trigger.   

dave

[Clint]

Dave,
If you are going to provide more info on this lock, I would be interested in the thickness of the lock plate and the thickness of the flint cock at the pivot hole. Also the thickness of the tumbler. There is lots of data on general lock configuration, not so much on material thickness and height of the bolster. Most of my locks tend to be a little thick ( .160" - .175 ") as I am looking for a firm thread base on wrought iron plates.
R/S Clint

[smart dog]

Hi Clint,
I will do more than that.  I'll post those dimensions for several English locks from different periods.

dave

[Bob Roller]

The profile of this lock is nearly identical to the Nock/Bailes I made for the shop
of Helmut Mohr in Germany.I owned these moulds for the plate,cock and frizzen
and gave them to Les Barber and Larry Zornes to use for any project they might be
compatible with.It is also close to the current L&R small Manton.The REAL lock is
the mechanism on the back of the plate and the "engine"is a mainspring preloaded
to give abrupt acceleration to the cock when the sear releases it.My lock making days are
over and other than Jim Kibler is anyone making a lock with the "anti friction swivel"
and a powerful mainspring?A stiff spring is frequently just that,stiff.Hold the sear up
and pull the cock back and forth and there should be an "oily"feel to it with no noticeable
drag from the mechanism.
Bob Roller

[Pukka Bundook]

Bob,

You are dead right on the "Oily" feel of a good lock. No friction at all is felt.
I believe it was Col. Peter Hawker, who first used the term, "oily".

[smart dog]

Hi Guys,
I am so sorry this took so long but I was incredibly busy with finishing the Edward Marshall rifle but also reviewing a very large science book for the author.  I am supposed to be retired.  I also wanted to add a bunch of data to this thread that may be useful to some who obsess about locks like me.  To others it may be over the top but there it is anyway.  In this post I just want to add info for Clint and respond to Jim Kibler's previous response. Then in a second post I am going to add a bunch of new pictures and a plethora of measurements of the tumblers, sears, bridles, and mainsprings from 2 fine English locks. 

Clint, here are the measurements you asked for on the Mortimer lock.  The general thickness of the lock plate is 0.123".  The thickness of the plate with bolster measured directly behind the pan is 0.265".  The thickness of the flintcock at the tumbler screw hole is 0.125"  I will measure more lock plates and flintcocks for you a little later.

With respect to Jim's comment, our disagreement is not about geometry because I understand this stuff as well as he does.  Where we are talking past each other and with Stophel is what constitutes a full cock notch that is too deep but that keeps the sear in the same vertical position at half and full cock. So here are some data from 2 fine English locks.  On the Mortimer lock the distance from the tumbler spindle to the lip of the half cock notch is 0.395".  The same measurement for the full cock notch is 0.410".  The depth of the full cock notch is 0.037".  I measured another lock by Field, which is a very late flintlock era lock.  The same measurements are 0.473", 0.484", and 0.06"; respectively.  The depths of both full cock notches are deeper than the thickness of the tooth on the sear.  I cannot measure the Mortimer right now because I don't have the triggers.  They are being browned with the other hardware and barrel by a gunsmith out west.  I'll have them soon but I do have the complete Field fowler and the trigger pull is crisp, no creep at all, and measures 2.8 lbs.  The sear spring is very stout so I could reduce it and create a trigger pull around 2 lbs as I have on guns with locks I've built that did not have flies and had well behaved sears with no creep and crisp let off.  My current favorite rifle is one of those.  However, I would not go much below that because it would risk the sear engaging the halfcock notch when fired, which is why fly detents were added.  My point here is that the "deep" full cock notch that Stophel and Jim assumed would be bad for performance does not have to be unless you want a trigger that performs like a set trigger.  Then you need a fly.

dave