In the past year, I experimented with 220 gr. bullets in my Glock 20, and found that they simply could not be made to work. Without re-hashing the whole thing, I came to suspect my slide velocity was too high due to the very heavy bullets. One possible solution is a heavier-than-stock recoil spring. The Glock 20 comes with a 17 lb. spring. Wolff Gunsprings offers replacement springs in various increments, up to over 20 lb. I have to buy a metal guide rod + one or more springs. I have no idea which spring will do the trick, so I pretty much have to buy the Wolff "calibration" package, which includes various levels of stronger-than-stock recoil springs. I suppose I could buy increasingly stronger springs, one at a time, until I find the one that works. But it seems more economical - and less tedious - to buy the multi-spring package instead. With my luck, I'll find that the first increment (19 lb.) does the job. Any thoughts on what to do with the leftover recoil springs? Please comment if you've put an extra-strong recoil spring in a Glock 20, or only thought about doing it.