What if...
On the P50 mags made by ProMag. What if the spring in the magazine could be retracted like some of the 22 caliber magazines?
A thin 3mm wide cut in the top to bottom areas of the magazine. Running only about 3" from the bottom of the magazine towards the top. Add a steel pin secured on the top with an abrasive flat surface and do the same on the bottom side. Making sure that these flat areas are not protruding past the plastic rails of the magazine.
You would take both thumb and first finger and draw down that spring, which reduces the pressure put on the entering round. Thoughts?