I've become a believer in the DPM system. One of the pistols I own is a CZ 75 steel railed compact in .40. These were produced around the year 2004 and I am not sure how many were produced. This gun had become known as the 'problem child' for me since it seemed to have trouble behaving. I bought it used and it had issues feeding. I figured that I'd tune it but it didn't take well at all to Cajunization with more issues than ever. Extra power mag springs helped and a restoration of all springs to factory spec helped more. Running a 22# recoil spring and stainless guide rod helped a lot more and brought it up to about the 99% level. Still, not good enough for carry though.
After reading this thread, I thought I'd give a DPM Systems Recoil Reduction System a shot and ordered one for a CZ 75 Compact. The problem child lived up to its name and destroyed it within 10 to 15 rounds. I contacted DPM (they are in Greece) and they immediately responded with both phone calls and emails to try to figure out what happened. Photos and measurements went back and forth, all with their reassurance that if I was not happy, just let them know and they'd issue a complete refund. We figured out the issue and it was that batch of .40 Compacts produced by CZ over a decade ago. Turns out, the spring house is significantly shorter on those guns than on other 75B Compacts. The short spring house was allowing the inner sleeve to take the impact of recoil and it took very few rounds to deform it. DPM offered to build a custom system for that gun and if it still did not work, issue a refund. I took them up on that offer and they sent not just one replacement for the odd compact, but a second one for another 9mm compact I have, with no additional charge.
I received the new system and have run it for a bit and the thing works. That compact .40 now feels like a stout 9mm and the gun finally runs. In fact, it runs very well now. I still have the factory springs everywhere else in the gun, so over time I'll take another shot at cajunizing the pistol. The second recoil system that they sent for my 75B compact has made that gun feel a bit better than my 99021 in recoil feel. Anyone who has shot a 99021 along side a standard steel compact knows how sweet the 99021 feels due to that extra bit of weight up front. The DPM system does seem to make a difference.
The thing that I was really impressed with though, was the high level of customer service. Not only did DPM stand behind their product, but they went well above and beyond what was called for. Over time, I'll add their system to a couple of other guns to see how it effects them. Next up may be either a full size 75B, SP01 or Glock 23. If the difference in the G23 is as dramatic as it was with the .40 Compact, it will really become a nice winter carry gun.
BTW, they do custom work as requested and I am now wishing that I still had my 10mm Witness. That would have been a fun one to try their system on.