First test the tension of the mainspring by putting the gun on a bathroom scale, and noting the weight of the gun shown on the scale. Then slowly cock the hammer back to full cock, keeping an eye on that scale. Note the maximum weight shown on the scale when you get the hammer to full cock. Repeat it three times to get an average. Now you know where you are beginning.
Yes, you have to cut coils. Remove the lock from the gun, and cock the hammer back to full cock. If it is a typical lock, the spring will stack coils, that it will compress fully, and still require more movement to reach full cock, so the coil spring will start moving sideways like a rattlesnake. All those extra coils are great to protect companies from product liability suits, but lousy on nipples, and accuracy. The first thing to do is remove enough coils to stop the stacking. Then test the spring again. note the tension by subtracting the weight of the gun from the maximum reading you get when you cock the gun to full cock. If it is more than 10 lbs. you can continue to cut coils. Most exceed 30 lbs. When you get the tension down below 20 lbs. you will begin to sweat. Everyone does the first time you do this. put the lock back in the gun put a cap on it, and fire it out in your garage, or back yard. Satisfy yourself that the spring is still going to fire the gun. You will notice how much easier it is to cock the hammer, now. take the lock back out, remove the spring and continue to remove coils. Begin testing the spring tension after each coil is cut.
I know, this is a lot of putting the gun back together again, and then taking it apart again, but its necessary. Unless you have some sohphisticated equipment to test the spring tension of light coiled srpings, this is the way it is done.
When you put the gun back together, go ahead and fire off another cap. When you get it down to 15 lbs. you may want to stop for the day, and give your nerves a day to recover. Put the gun together and clean it, and put it away for a day.
Even with the old nipple in place, you want the face of the hammer to hit the nipple evenly all the way around. Use some lipstick, or marking dye to coat the top edge of the nipple and then lower the hammer down onto it. cock the hammer back and check out the dye that has transferred to the face of the hammer. If you see a full 360 degree ring of the same width on the hammerface, the contact is correct. If not, you have a high spot, and you need to grind that down. Use a grinding bit on a dremel tool at modest speed to grind away the metal on the face of the hammer where the dye IS. The law spot is where the dye isn't! When you have removed all the dye, test it again, and repeat this process. I use a folded over piece of paper towel between the nipple and hammer, and fire the hammer. It should almost cut a punch hole in the paper. I " cured " an percussion gun I had years ago that would not fire the cap on the first hit doing this, and friends were amazed that I had stopped fussing with my caps and lock at future shoots. Most wanted to know what I had done, or had done by someone eilse to fix my piece of junk!
paul
