I'm a 10mm fanboy, my 20.3 was my usual edc when I lived in Montana and I'm desperately trying to recall a single malfunction with any type of ammo. I ran a bunch of different Double Tap loadings through it back in the day and still have two boxes of their stout 200gr flat point gas checked rounds that fed without a hiccup; you definitely knew you were shooting them, but they were far from unpleasant.
Someone on the old Taffin forum directed me to a custom loader (whose name is lost to me) that made up very nice loads using Silver Tip hp's running hotter than Winchester boxed and sold them...I wish I had a case of those. I kept one of those in the chamber at all times and swapped mags between the custom ST's and the 200gr DT's for town and field carry respectively. The 29.3 I briefly owned hated both those loads.
I got a bit hot and bothered with thoughts of a 29.4 stoked with the Lehigh Extremes until @GJM related his repeated reliability issues with that combo. Sigh...still want a 29.4, you know, for reasons.