Buy a mainspring vise from any of the suppliers. I rarely use mine anymore, and use a visegrip instead, but I have taken lots of mainspring off locks safely and know what I am doing. I also know what NOT to do. If this is your first, you have not climbed that learning curve, yet. Buy the mainspring vise.
You second question is a series of questions. Disassemble the lock-- in this order:
1. Remove the mainspring.
2. Remove the frizzen spring if a flintlock.
3. Remove the sear spring.
4. Now remove the frizzen, on a flintlock, and set it and its pivot screw aside, together. Put it next to the frizzen spring. They are a working UNIT of the lock. Keep them separate.
5. Remove the bridle. It holds both the tumbler and the " fly" on the tumbler that helps the sear go over the half cock notch. Put Tape on that small fly before removing it, and tape it to something you can see in front of your face as you sit at your workspace. ( A clear glass or plastic jar will hold onto this little bugger! When I am satisfied that the tumbler rotates smoothly in its lockplate hole, and am done with any polishing work on it, or the notches, I tape the fly to the tumbler and set them aside with the cock. The bridle goes with the tumbler, too.
6. Now you can remove the sear bar, and its pivot screw. But while its in the lockplate, now is the time to move the sear in and out of the half cock, and full cock notches in the tumbler, and see if there truly is a fitting problem. Being able to move the parts manually and See where they go ( with the bridle removed) helps to decide if their really is a problem or not.
7. You remove the tumbler FROM THE cock, not the cock from the tumbler. Use a properly sized, thin screwdriver blade to back out the the screw that holds the cock to the tumbler. Only back it out a turn or two, but not all the way out. Now, put a piece of scrap wood on the head of that screw, and with the lockplate set over the separated jaws of your bench vise, or over two blocks of wood spaced apart on the bench, use a soft hammer head to tap the cockscrew to force the tumber Out of the hammer square. Once it releases, you can stop and unscrew the cockscrew completely. Put a "witness mark" on the tumbler stud, and the hammer, so you know which flat of the square stud fits which flat of the cock for reassembly. Now, just use a soft Metal( copper, aluminum, brass, plastic, etc.)rod to tap or push the tumbler off the cock. Have a soft cloth under the lock plate to catch the tumbler so it doesn't fall to concrete flooring and get a dink on it.
Without seeing the actual lock parts, its impossible to tell you if the nose of that sear bar is too long. That is normally determined by the depth of the FULL cock, and HALF cock notches. If the notch is too deep, you can get a long, harder trigger pull than is desireable, but that condition is fixed different ways, depending on the trigger used, how polished, or unpolished the notches and the nose are, etc. Normally, the nose of a sear is NOT shortened. Again, its possible to have a sear nose too long, but rare. I would want to see the lock before ever recommending that the sear nose be shortened.
I have an article on shooting and tuning the flintlock, republished under "Articles" at the Member Resources section at the top of the index page to this forum. While it addresses flintlocks, all the parts on the INSIDE of any flintlock are very similar to those found on the inside of a percussion lock. You can ignor all my comments on how to deal with the frizzen, and frizzen spring, if you're shooting a percussion lock. The advice about the internal parts works for both percussion and flintlock actions.
YOu can go to Bob Spenser's Black Powder Notebook, to get a good picture of the lock parts, and their names, and relationships.
http://members.aye.net/~bspen/percterm.html
If you go to his index page, you can find the information on both the percussion and flintlock actions, as well as great articles full of information you need to know.
http://members.aye.net/~bspen/index.html
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The lock is fully disassembled, now. If you set the parts you remove together with the screws that hold them to the lockplate, you won't be using the wrong screws. If you use the three springs on a flintlock, or two on a percussion lock, as the focus of the three functional areas of any lock, and organize the parts of the gun to the spring that makes them work, reassembly is easy, as is working on each part of the lock.
As to whether to use one or two lock bolts on the action, you need to find pictures of the gun you are replicating, and stay with that. They will also tell where the lockbolts) go. Look at the Bob spenser material to get a general idea of where you want your lockbolt to be.
The top one should be as close to the tumbler as you can get it, since the tumbler is under the most tension. If a forward bolt is use, its almost always placed just forward of the frizzen spring, between the barrel and the Ramrod channel. This allows a tapered ramrod end to fit under the forward lock bolt and all the way back to where the end of the barrel meets the face of your breechplug.
I hope this helps. :thumbsup:
