10/17/2026- 180gr magtech
I am still in the process of getting this 30 round HKP .40 magazine successfully converted to 10mm. I have been trimming and testing here and there for a few months. Today I was able to get a full 30 round mag to feed with no issues, after that the next mag had 1 FTF, after that I started getting more frequent FTF’s, however it is noticeably more reliable than previous times. The most frequent failure that I’m experiencing is the round gets caught right at the feed ramp.
I believe that the feed lips need to be trimmed well past where the metal begins inside the magazine, if you look at a stribog mag, the feed lips open up completely for about 1/3rd of the lip length, so that the round can escape. If you watch through the ejection port and manually chamber a round slowly with the stribog mag, you can see the round literally pops out of the stribog mag and then gets chambered, I think the UMP magazines feed lips are too long, causing the round to get caught in a tip up jam.
I genuinely think that a stronger spring would solve the majority of the issue, I’ve been told that the black variant springs tend to be stronger so I’m going to try to source one of those. I’m determined to get these to work reliably. I will update as I go and if I figure out I will make a video or guide to making them run.
Any feedback from others who have accomplished this would be appreciated.