I bought a 581 series as my first centerfire rifle. As such, I was committed to it (nowadays I probably would have passed it on down the line). Anyways, in factory form it wouldn't hold more than a 6" group at 50 yards, with a scope. Handloading cut the group sizes down to about 8 MOA. Into AK territory, but I wanted more. I then sent if off to
www.greatwestgunsmithing.com for his accuracy package. He did one heck of a trigger (about 1.5 lb with no creep), glass bedded the action, shortened the barrel to 17.5" and threaded for an AR muzzle break (I went with the Smith Vortex brake), installed a buffer on the op-rod, and sent several different sizes of orifices for the gas port. When it got back I milled out the forearm for a sling swivel stud to attach a bipod. After some more load development, I have a Mini-14 that holds 1 MOA for as long as you care to shoot it, flings the brass about 7 feet all in one spot, and is so loud that it still rings a little with double hearing protection. It is still very sensitive to load - some shoot 8 MOA while the good ones shoot 1 MOA.
My choice load is the Hornady 60 gr SP over a near max charge of Varget. The XM855 military load is good for about 1.5 MOA. It is worth noting that I haven't got it to shoot anything less than 55 gr or greater than 63 gr very well at all. Flat base typically shoot better than boat tail. It also likes the powder charge on the high side. You pretty much have to get to 223 max charge before it starts shooting well. 556 level loads typically shoot better.
Now that I realize how easy it is to build an accurate AR-15, I probably wouldn't mess with the Mini. That being said, the Mini does have a very addictive feel and sound of that heavy steel gas action clanging around in the solid walnut stock every time you pull the trigger. I think it's more fun to shoot than an aluminum and plastic AR.