Hi,
I thought I would give you folks a tour around a fine 1785-1790s English lock made by a top London maker. H. W. Mortimer was one of the best makers in London during the last quarter of the 18th century and the beginning of the 19th century. He was unusual in that he was free of the gun makers guild but also the goldsmith's guild. He did a lot of his own decorative silver and gold work.
The lock probably is from the late 1780s and features a flat beveled plate and flintcock, guttered gold lined pan, roller frizzen, and tumbler with stirrup. The decoration is simple and includes some sparse engraving and Mortimer's name engraved within a gold inlaid panel. Even if the lock was finished bright, the dark running leaf border would make the gold name plate stand out. The tumbler bridle also is extensively engraved, something that was not uncommon on higher quality guns. The lock plate and flint cock feature nice "ovolo"moldings typical of better flat-faced English locks. British makers borrowed that design from the furniture and architectural trades.
Looking inside, you can see the wonderfully engraved bridle. The mainspring is itself a work of art. The long lug or tab on the upper leaf positions that leaf low relative to the bolster. That allows the lock to be mated with large barrels without the spring breaking into the barrel channel. Note that the lower leaf gracefully tapers in thickness. When the lock is brought back to full cock, the lower leaf is straight and the main bend pinched. That shows the entire spring is working rather than the main stress happening at the middle of the lower leaf as in the modern-made lock shown below.
As the lock is brought to half cock, look how close the pivot on the bottom of the stirrup and within the claw of the mainspring comes to the axle of the tumbler. At full cock, it is very close giving the mechanism very strong mechanical advantage. Also note how little the spring moves upward from half cock to full. There is a bit of let off in force needed to bring it to full cock. The lock requires 6.7 lbs of force to bring it to half cock and 6 lbs of force to bring it to full. In contrast, for the modern-made lock showed previously, the force required to bring it to half cock is 9 lbs and 10.2 lbs to bring it to full. Note how robust the stirrup is on the Mortimer lock and it is pinned to the tumbler with a tiny screw rather than loosely sitting in a yoke.
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.
That prevents the sear from slipping into the half cock notch when the gun is fired. Some modern locks have that relation reversed and rely on an overly large fly to push the sear away from the half cock notch. You often will notice excessive wear on the tip of the sear where it rides over the fly on those locks. The bridle, sear, and tumbler have friction reducing collars. However, I believe the height of those on this lock is over kill and likely a marketing gimmick more than anything else.
The frizzen has a roller bearing in its toe, a feature that became popular in the late 1770s and 1780s. Later locks usually had a roller mounted in the spring. For its size, the frizzen is thick, which I believe adds mass and enhances sparking.
It requires 4 lbs to open it, which is about 69% of the maximum force required to pull the flintcock back to full from rest. That is a bit stiffer than I usually try to achieve on my locks but the proof is that this lock really sparks!
By the time this Mortimer lock was made, the styling of British sporting guns changed from what we often think of as the classic mid-18th century British gun. Combs were lower, butt stocks smaller, locks smaller, and almost always flat faced on anything but military, cheap livery and trade guns. Wrist checkering was evolving. It is a great lock and represents top of the line work by a great maker.
dave
