Almost all my reloads are of carefully-made Milsurp-equivalent ctgs. These M193 and M855 replica ctgs are considered a bit on the "hot" side, compared to most civvy ammo, but still well within the capabilities of the Mini.
They being carefully-made handloads, my ctgs are far more accurate than GI Milsurp.
Broadly speaking, it's mostly about obtaining high-quality bullets, meticulous case prep, and dropping very accurate powder charges. It's possible to do the latter stuff on a well-set-up progressive press, but the case prep takes some time and effort.
I did reduce the size of my Mini's gas port from outrageous OEM gas port ID. IIRC, probably the .040 ID unit. I bought the whole kit, so I could have options.
The only way to ensure your Mini will function properly with a reduced size gas port is to test the Cold rifle, with Cold ammo on a Cold winter's day. Everything as Cold as possible!
When in doubt, go larger gas port. Some Minis used to come with gas ports identical with those used in Mini-30s, and so wildly over-gassed.