Although I have never had any problems with the M-21 coil mainsprings and they are always under some compression and many have been that way for 60 years,I have problems with newer springs. The Citori and 680 series Berettas,if fired in competition (15,000 shots per year) shorten 3/16" after two years (mainsprings)and with a simple replacement,function as new.The older guns have large diameter wire and ,if they lose strength, still have enough power.While the newer guns use smaller diameter wire and take a noticeable set in a much shorter time.
