Did you say (won't be able).... I'd hate to have to grab the low E flat wound guitar string off my Strat and make one.I'm a recent mechanical engineering grad. I did spring design for car door handles (torsion springs specifically) during a summer internship, so I learned more about springs than most people would care to
You won't be able to much of anything about the hammer spring. Square wire springs produce much more force than round wire springs, and are less economical to produce.
OK, just what we need...a spring expert. I understand that flat/square wire is the best for torsion springs. Where I am going with this hammer spring is in the trigger job thread. My concern is that the existing hammer spring places unequal pressure on the hammer since the leverage is off center. What do you think about that idea? Then take the double torsion spring that is fitted to the trigger/trigger bar and imagine a hammer spring of that shape but of the proper length, coil diameter, width, etc. I have no idea how you measure the torque it takes to wind one leg of the P22 hammer spring from free rest to the position the cocked hammer moves it. I do know that hooking a Lyman trigger pull gauge to the hammer requires 8 lbs of pull to cock the hammer with a new spring. I have purposely overwound these springs to a new set but didn't do this scientifically....like mearsure just how much rotation I did to acheive a new at rest angle. I just did it by feel. At 7 lbs everything is fine. At 6.5 lbs.....light firing pin strikes begin to occur.
Off center pressure.....real or not with the P22 torsion sprin? I'm concerned about this regarding hammer and sear work. Below is a Walther manufactured double torsion spring in a P38. It appears to be of round wire. If it was good enough for a P38, it would be more than good for a P22. So can something like this be fabricated for the hammer spring so the forward pressure is even on the hammer and frame? Glad to have you join in this discussion. I'm a landscape architect and have no engineering background at all. I do know what passivation is thanks to MG Mike using that big word. Had to look it up.... M1911