I've been experimenting with different recoil springs for my Combat Master. The original springs felt very limp, with almost no pressure to hold the slide in battery. The gun would run for 20-30 rounds, then start to malfunction as it got dirty. I found the dual spring set-up that King's Gun Works sells for their Officers guide rod kit was a drop-in. The springs are the proper length, and the rate seems to be perfect for hardball-equivalent loads. 500 malfunction-free rounds, twice in sessions of well over 100 rounds, prove the King's springs. I also bought an innovative "flat wire" spring from Integrated Systems Management, Inc. (ISMI), and this might be the best spring available. Also intended for the OACP, this spring is guaranteed for life! I changed out the King's springs after about 500 rounds, so a life-time guarantee is some claim. The inside diameter of the spring is perhaps just a little too large for the Detonics guide rod, allowing the spring to snake some as it compresses, but some correspondence with another Combat Master owner (thanks, Bob), has revealed an uncataloged ISMI spring with an even smaller inside diameter than the one that they usually sell. This might be the hot ticket. The spring that I do have provided quite a noticeable improvement in in-battery pressure on the slide, without a higher overall rate than the standard round-wire springs. Maybe if enough Combat Master owners contact Marc at ISMI, this experimental spring will make it into their catalog as a Combat Master replacement. www.ismi-gunsprings.com