Overview of gun locks

Flintlocks

Developed in the mid 17th century, the flintlock soon replaced its more expensive and complicated predecessor the wheelock.  As with other firearm innovations, the flintlock evolved over time often reflecting sophisticated refinements.

The lock shown below by Rigby of Dublin in a good example of the flintlocks development by 1800.  By no means do all locks of this period reflect the quality and workmanship shown here.

Lets have a look.

The lock shown has two external features often found on locks of the 1800 period, a rain-proof pan and a roller on the frizzen spring.  When the frizzen is in the down rearward most position, its bottom shape neatly covers the flash pan leaving a recess front and rear of the pan.  The roller on the frizzen spring acts to minimize friction with the foot of the frizzen and most importantly to precisely regulate the action of the frizzen.

A close-up below of the frizzen and frizzen spring relationship illustrates the function of the roller.  Notice that when a straight line is struck from the center of the frizzen screw  thru the center of the frizzen foot and thru the center of the axle of the roller, the frizzen is at neutral.  Just a few degrees of movement of the frizzen foot causes the spring over center and forces the frizzen in that direction.  Notice the recesses to front and rear of pan.

 Below the inside of the lock is shown, notice that the lower limb of the mainspring when under maximum pressure at full cock is perfectly straight.  The spring has been “balanced” by carefully filing a uniform taper both in height and thickness.  The fancy pierced and filed bridal surface while aesthetically pleasing has no function.  The internal parts are all casehardened and most are polished to the mirror finish, this finishing treatment is very resistant to corrosion. You can also see the inside view of the rainproof pan.

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   Percussion  locks

A back-action percussion lock. This style lock in its earliest form dates to 1835-40.  Most commonly found on single fowling guns and double barreled shotguns.  The back-action lock stayed in use through the entire percussion period and later evolved into widespread use in cartridge shotguns and rifles.

Notice the following details. 1)a three screw bridal with the sear pivoted on a stud. 2) lock is in the full forward position and the tip of the mainspring protrudes above the lock plate. On a well fitted gun the hammer will contact the nipple just before full forward, thus the spring protrusion is eliminated. When removing locks from a gun, it is always good practice to bring the lock to half cock. By doing so the tip of the mainspring is lowered well inside the lock plate resulting in ample clearance from the lock mortise in the stock.

This lock plate has been arched or curved in order to conform to the wrist proportions desired by the gun maker. The mainspring is also fitted to the curvature of the lock plate.

Fitting two back action locks into the stock of a double gun requires removal of a considerable amount of wood in the wrist area. Some consider this removal to inherently weaken the stock of such guns.

A ‘4 screw’ bar lock.   Locks of this style and quality reflect the pinnacle in the evolution in percussion locks. Flawless workmanship and artistry in filing and polishing are blended with perfect mechanics and geometry. Truly a meeting of form and function.                

The tumbler and sear are ghosted, i.e.. small bearing shoulders are turned on each side of the respective pieces so that only a small portion of each directly bears on the inside of the lock plate and bridal. Virtually all friction between these parts is eliminated.

The sear is suspended on a stud between the two rear screws. It is free to pivot because the feet of the bridal are .001 or .002 taller than the thickness of the sear.

Notice that traces of the casehardening process are still apparent. This makes the various parts glass hard on the surface giving good wear and friction resistance.

Above, the bridal screws have been removed from their respective holes. Notice the file slashes on the screw shanks. From the left, one slash then two, etc. Each screw was fitted with regard to overall length, thread length, taper on the shank, and taper on the head. All of this was done while the lock was in the ‘white’ and unhardened. Finally the lock was disassembled and the parts casehardened. The file slashes are merely a simple way to replace the screws in their fitted hole upon reassembly.

Joseph Brazier, Ashes identifies the lock maker. Brazier locks are found on almost all high quality arms, he being the premier lock maker of the period. Other Brazier marking are ‘I.B.’, J. Brazier, and Joseph Brazier Ashes-Wolverhampton. These locks were sold to the trade in the white, unhardened, unpolished but fully functional. Gun makers specified the lock plate shape in some cases.

Below, another “4 screw” bar lock variation by Stanton (ca. 1865) which was used by Charles Ingram on a target match rifle.  Bridal is of a different shape than used by Brazier but the mechanics are virtually identical.  Stanton’s work is also of best quality, look closely at the fit/relationship of the sear at 1/2 cock and the fit of the interrupting ‘fly’.

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Outside surface of the lock shows only the gunmakers name.

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Lockmakers marking shown above.

The common 2 screw bar lock.   This is the type and quality lock found on many ‘trade’ or ‘hardware’ guns.  These were produced in great quantities in Birmingham England and imported into the U.S. often with the name of the retailer already on them.

These locks have the sear pivoted with the rear bridal screw. In this case, the screw cannot be fully tightened because the bridal will bind and retard proper movement of the sear.  Often these locks are found with excessive tolerances, indifferent shallow screw threads, improper part relationships, and unhardened. 

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Above, notice the 4 pins or screw ends on the lock which is unembellished and the 2 pins on the lock which is engraved.   Don’t be fooled by engraving, these are external views of the locks discussed previously. When looking at a shotgun or rifle as a prospective buyer, the presence of a 4 pin lock is usually accompanied by a name and complete address on the rib or top barrel flat.  These factors are good indicators of high quality and superior workmanship.