Thel/lone star, As a gunsmith for many years and knowing a slew of gunsmiths over the years, I can count on less than one hand, the number of gunsmiths I've known who had a spring testor. A good "commercial" one and not a piece of "homemade" junk! What you do after working with hundreds/thousands of springs is develope a "feel" for springs. Is it an exact science? No, but it works! A good gunsmith will be able to fashion lighter weight springs for you. I "suggest" you also bring him a good supply of all the ammo types you will be using in that GP-100 for his "testing".....................Dick :wink: