I have a mini (series 181-XX) that had the same problems. Seems most do to start with. 2 inch to 4 inch groups were the norm. Then I glass bedded mine, added a scope and muzzle break and handload 55 grain bullets with 25.0 grs of IMR 4895. That was 5 years ago. Maybe mine's "RARE" but it shoots continual groups that fit in a 2-bit piece at 100!
You might check out this site for more info on the Mini from a LOT of folks that have them, problems and solutions included......
www.perfectunion.com/forums/index.
Nope, It kinda sounds like BUT it's not a "Lonely Hearts Club" HA!!!
Best of Luck to ya,
RR