Gallahad,
I've tried as many as 10 different types and brands of 22 ammo in several different MK IIs. None of the bulk stuff shot too well in mine. I did find one that shot well in all the MK IIs. It was CCI Pistol Match. It's not bulk ammo and although it's not the cheapest, it's not the most expensive either. The second best, that I tried, was Winchester Power Point.
Best,
TnNuc