I have "fixed" Cochrans, Silers, L&Rs, and a variety of foreign made locks that can no longer be sent back to the factories. Some were sold through American companies, like Dixie Gun Works. Many were made in Italy, Spain, Japan, and some in countries of unknown origin. I treat locks made? in India, or Pakistan to be in this category. I have also worked on locks on Belgium made Dbl guns.
If something is under factory Warranty, and the company still honors that warranty( a big IF these days?), why would I tell someone to spend money for me to fix their lock when it can be sent back to the factory and fixed for free? ( Yes, I have had people who sent their locks back to be worked on and were not happy with what the factory did come to me and ask me to work on the locks for them. Only under those circumstances will I work on such locks.)
The first thing I do to reduce mainspring tension is to make sure that no moving part of the mainspring ( Usually the bottom arm) is rubbing against the lock plate. That requires a line of sight inspection of the lockplate with the mainspring in place. I want to see a "sliver of daylight" between that arm and the lock plate. Sometimes the plate is bent, and must be straightened; other times, burrs and sloppy casting had metal on the arm rubbing against the plate. That has to be removed.
Second, I do a similar check of the tumbler, with the mainspring, and the sear spring removed. I want to see daylight between the inside of the tumbler, and the plate, and FEEL ABSOLUTE FREE movement. If there is any grinding felt or seen, work has to be done.
Third, I check the clearance between the bridle and the tumbler. It also must be free of burrs, or any casting flaws that permit the tumbler to rub against the bridle.
4th: I then check the sear spring to make sure its working freely, and correctly.
5th: I check the sear, to make sure its Not rubbing against the lock plate.
Any drag of these moving parts puts tension against that tumbler, and gives a false idea of how strong the mainspring is. Getting all those parts to move like glass on glass is required before measuring the tension of the mainspring.
Now I measure the tension of the mainspring. Most factory Bess springs will have tension over 30 lbs, and some more than 40 lbs. That is, it takes 40 lbs. or more pressure on the cock to move the cock from the down to the FULL COCK position.
A. I now take the lock out of the stock, and watch the mainspring as I cock the hammer back to full-cock, to see what is going on, and if the mainspring is binding at some particular point in the cocking. I look at the contact between the end of the HOOK and the horn of the tumbler. I examine the horn to see how smooth, or how rough that surface is. I check the shape of the hook, and where it "sits" on the horn with the hammer down, and with the hammer at full-cock. Not all HOOKS are created equal, nor are most horns.
B. I look to see if there is stacking; ie. is the lower arm forced to go past a point where the two arms of the V-spring are parallel. That is the fastest way I know for these spring to break eventually.
C. I look at the Tab at the top of the upper arm, to see HOW LONG it is, compared to the depth of the slot in which it fits, and how wide the tab is compared to the width of the slot in the bolster. I put dye on the tab to get a better idea how much of the tab actually goes up into the slot.
Obviously, this requires removing the mainspring, and replacing it, several times. I have several different tools to use for this purpose, depending on the size of the lock, and size of the mainspring I am examining. The standard Mainspring vise I bought years ago from Dixie GWs still does the job on all the large locks.
TRICKS: to reduce mainspring tension with the MINIMUM amount of removal of metal:
1. First I don't want to see a mainspring lower arm bending in an arc, which indicates that there is a thin spot in the spring arm. That is going to be a weak spot, and is a defect in manufacturing. I want that arm to move as a whole unit from the bottom of the V to the base of the hook.
2. If that proves to be the case, then radiusing the edges of the lower arm on both the back and front faces will help the metal bend better, without creating stress fractures. I do this with a fine file.
I then put the lock together back into the stock, and measure tension again to see what little has changed, if any.
3. I use files to bevel the edges on both the inside and outside edges of that lower arm, to reduce the strength of that arm tension. I draw file along the whole length of the arm. Some of those foreign castings have a huge amount of metal at the bottom of the "V", and that will make it more difficult to get the spring to flex properly. So, I grind away the excess, leaving enough metal so that the bottom of the V is no more thick than 1.4 times the maximum thickness of either arm as it separates from the other at the bottom of the "V".
If the mainspring stacks, then there are several other "tricks" to consider. For instance, if that tab is not going all the way into the slot, I draw file the curved top to see if I can't get it to go all the way in. Then I check to see of this small movement of the upper arm "opens" the V enough to stop the stacking. If not, I see if the tab can be shortened, and thereby change the angle a bit as the mainspring is mounted in the lockplate, and thereby stop the stacking.
If that doesn't get it done enough, I re-shape the HOOK at the end of the lower arm, either by filing the end, or heating the hook up enough that I can close or open the hook as needed to change the angle at which it rubs against the horn of the tumbler. I use Vise grips to hold the mainspring RIGHT Behind the hook, to act as both a Heat Sink, and to allow me maximum control. I use a 1/4 diameter piece of steel rod, or iron pipe( if you can find it that small, still) to open or close the arch of the HOOK.
Because stacking puts so MUCH tension on any v-spring, I like to attend to this work BEFORE I remove any metal from the mainspring itself.
4. I also reshape and POLISH the heck out of that upper, inside curve of the horn on the front of the tumbler. Not only will proper shape and finish reduce friction , but the arc of that horn can be used to speed the FALL of the cock after the cock comes over the top of its arc. This helps to speed hammer fall, and also increases impact speed of the flint edge to the face of the frizzen, so that you can get more sparks with less tension on the mainspring.
5. When someone wants a flintlock that has a light hammer fall for serious target shooting work, I can create a slightly thinner" wrist" directly behind the HOOK, so that this short part of the mainspring arm bends a little more than the rest of the spring does. ( This runs contrary to my desire that the whole length of the lower arm move as one piece, but its done for a reason, and the change is so small that I have not had a mainspring fail at this point.) That short end of the mainspring arm "Whips" the tumbler forward faster towards the end of the fall, allowing greater speed and force to drive the flint's edge into the steel to cut sparks.
This only works if the Angle of Impact of the flint to the frizzen is at 60 degrees, and the Point of impact is about 2/3 of the distance UP from the bottom of the frizzen. With the correct angle, and lightened spring, you get good sparks, self-knapping with each strike, making a new sharp edge for each next shot, and you get longer flint life.
You also have to lighten up the frizzen spring( Or shorten the cam on the bottom of the frizzen, and polish the heck out of the contact points), so that there is very little resistance to keep the frizzen from popping open when its struck by that flint's sharp edge.
Too much mainspring tension, and too much resistance by the frizzen to opening up quickly, and you crush expensive flints.
If you have used flint and steel to throw sparks into charred cloth, or tinder a few hundred times, you will quickly learn that it doesn't take a lot of strength to make sparks, and you don't have to destroy whole chunks of your flint to get a fire going. The same principle works in flintlocks.
So, figure out what your objectives are for a particular gun and lock. This was what I wanted:
a. Quick, reliable ignition;
b. long flint life( I'm cheap!);
c. a light trigger pull;
d. a lock that didn't bruise my thumb when I cocked the hammer back.
e. a lock with parts that moved like glass rubbing against glass, as my customized revolvers, pistols, and breechloading rifles and shotguns do.
f. A lock that did its own knapping, leaving me to only watch how much the edge was wearing back from the face of the frizzen when the hammer is at half cock, before I move the flint forward in the lock, and reset the jaws.
Everything I do to a lock is helping to achieve those objectives.
If you disagree with my objectives, or think you know more about tuning locks, stop reading this, and leave me alone. I have only spent more than 30 years learning what I know, and I suppose I am as stupid as You think I am. I frankly don't care what you think. :shocked2: :surrender: :hatsoff:
