Hey man, this insane experiment of a thread finally got me to register for the site. I too tried to run a 365XL in CO for a good minute and ran into some of the problems that you experienced.

Now, I never used the 32 round mags, but I got good reliability from the 20 rounders by keeping them clean (just like you’ve been doing) and by using the OEM Sig 365 followers. I tried the Lakeline followers but those seemed to have too much drag and would get hung up on the last 10 rounds. Using the OEM followers improved feeding by a big margin

As well, the DPM recoil system with the lightest spring was the only thing I could find that allowed the slide to dwell at the back long enough to feed rounds reliably. If your coil-cutting experiment doesn’t work, then that might be something to look at.

Anyway, I appreciate your mad scientist approach to this problem! Best of luck