1. remove the frizzen screw and remove the frizzen. Examine the bottom of the frizzen " heel", which makes contact with the frizzen spring. If it is rough, file and polish it smooth. Don't file off that heel! Polish the surface of the frizzen spring where the heel contacts it, mirror smooth. Then put some grease, or a good thick oil on both parts and reassemble the frizzen in its bridle. drive in the screw, but don't push it in so much that it binds the frizzen.
Use a Trigger pull gauge to measure how much pressure is being put on the frizzen before it opens. Just hook the measure's arm over the top of the frizzen when it is closed, and pull the scale forward, keeping an eye on the scale. When the friaaen pops open, remember how many oz. it shows on the scale. do this several times to get an average. Most factory frizzen springs are TOO strong, and put too much weight on the frizzen. In addtion, the way many locks are put together, it is not unusual to see rub marks on the face of the lock plate where the upper arm of the frizzen spring moves up and down. If something is rubbing against the face of the lockplate, this adds further resistance to the frizzen. And, sometimes the heel is designed wrong, so that in pushing the frizzen open, the heel actually has to compress the spring in the process. The heel should be rounded on the front side so that the furthest compressed the spring is will be at the point where the frizzen is closed, and not when you are trying to open it!
Spring tension for a frizzen needs to be no more than 3 lbs. and 2 lbs. still does the job nicely. Remember, the only job a frizzen spring does is keep the frizzen closed until the flint strikes. That's it. Nothing else. The test for a good lock is to remove the frizzen spring altogether, and then spark the frizzen. If the frizzen still sparks well and the gun fires, you generally have a good lock.
2. Most mainsprings are too hard, although that will not create the problem you are now having. It does drive an improperly mounted flint into the frizzen, gouging out a groove or several, giving the face of the frizzen a washboard affect, if not corrected. That will cause the problem you now have. So, since I don't know if this is a new gun, or how many shots you have fired, CHECK the face of the frizzen. If it has grooves in it from the flint gouging out metal, you will have to grind the face smooth again, and probably temper the frizzen again. put the frizzen on a cookie sheet in your oven, at 350 degrees and leave it at that heat for an hour. Let it cool slowly by simply turning off the oven and letting it cool down over night. That should relieve any work hardening that takes place when you grind the face smooth.
A smooth face allows the flint to SCRAPE off metal and throw them into the pan, while the frizzen is in the act of opening. Measure the angle of impact of the flint to the frizzen. Using a plastic protractor, you can buy at the grocery store in the school supply section, put the center point at the exact point where the flint strikes the closed frizzen. Set the baseline of the protractor along the bottom of the flint, and then use a straight edge, - the side of a small piece of paper works- to run a line across the arc of the protractor from the centerpoint at the point of contact, to the inside top of the frizzen. That angle should be 55-60 degrees for best performance. If it is not, then you will need to heat up the gooseneck of the cock, and bend it down to the correct angle. This is not a difficult thing to do at home, if you take your time, use a propane torch, or Map torch, make a stencil or pattern to show the existing angle of the bottom jaw of the cock, and the new angle you want to achieve. Draw an outline of the cock, including the rounded bottom, after it is removed from the lock, and the top jaw, screw and flint are removed. Draw a heavy line extending past the top of the front of the jaw on a large piece of paper. Then use the protractor to find and locate the new angle you want to change the cock to. Draw that on the drawing. Then as you bend the cock, its a simple matter of holding the cock, in pliers up against the stencil or pattern, to check to see if you have bent the cock to the correct angle, or it need more bending. Take your time, and do this right. Usually, a change of only a few degrees are needed but the improvement in function is dramatic.
3. The flint should be striking the frizzen at about 60 % of the height of the frizzen, measure up from the bottom of the frizzen. If it strikes too low, the frizzen will not flip open. If it strikes too hight, the frizzen may open, but it may also be hung up on the flint when the flint buries itself into that groove it will create. When you set the flint in the jaw, do it when the cock is set at half cock. depending on manufacture, the bottom jaw should be parallel to the top edge of the barrel when the cock is at half cock, but some are set much further back. You can't do much about that without replacing the tumbler, and you don't want to go there. Just set the flint so the front edge is about 1/16" from the face of the closed frizzen when at half cock. If the flint is strking 60-70% of the way up on the frizzen, it will open the frizzen completely when it strkes it when the lock is fired. You can run the flint out so the gab between the edge and the frizzen's face is closer, but you don't want it touching at half cock, as that could interfere with the half cock notch as a safety measure for the gun.
