For ammo choices, do your research. Practice the art of Google-Fu, but remember YMMV, and you and you alone accept the risks of what YOU choose to do.
That being said, the report that was included in the box when my rifle came back from the factory, stated that it was test fired with proof rounds, and 20 rounds of Federal 55 gr. ammo. The report stated that the group was 1.25" and 6" high (most likely because I "upgraded" my rear sight to a Tech-sight, and sighted it in at 25M with lower velocity ammo).
A Google of Ruger Range Test found a video on "How it's made" showing Mini-14s being test fired on a 50yd range. So, I assume my rifle grouped 1.25" at 50yds. That's about 2.5 MOA, which is more than acceptable for my purposes. YMMV, etc., etc.