My understanding is that Accustrut sells a front mounted strut for the early Mini-30, that mounts under the barrel and considerably stiffens it up. Often, this will reduce the group size by 66%. These struts are not that expensive. I think about $125 or so.
Best part, if you are not satisfied with the results, you can return the strut to Accustrut for a full refund.
So, I would buy and mount an Accustrut, and then test fire some good quality ammo, not the cheap military junk that is so common. You may be surprised how well it shoots. And if not, then send back the strut. You will have lost nothing.
Regards, Mannyrock