I have 2 Minis. One has been worked over by Great Western Gunsmithing and shoots just over MOA. The other one is there now. If I ever decide to handload the 223 I expect the rifles to be MOA, each of them.
I have tried many 20-30 round mags, the only ones that work every time are the Rugers. BTW, Ruger made a factory 30 rounder some time back for their full auto goverment guns. I lucked out and got 5 of them, along with a bunch of 20 rounders in a trade a few years ago. They all still work fine.
Both guns have 16" barrels with a compensator and full stock bedding, one is a synthetic factory stock, the other a wood factory bedded job.