Finding Sub-MOA Factory Ammo
I handload but for just about every high power rifle I shoot at one time or another I've had to use factory ammo. I can tell you that in the (4) high powered rifles I own I've found factory ammo that shoots under (1) MOA at 100 yards for (3) shot groups.
In reloading I've found the most consistent factor in making Sub-MOA reloads has been velocity. My 30-06 likes 150 gr. bullets at about 2950-3000 fps. It doesn't matter if I'm loading Hornady SST's or Sierra ProHunters with RL15, IMR4350, or RL17. Once I get in that velocity range they group under 1 MOA. I've used both Lapua and Winchester brass with CCI & Winchester primers. As long as the velocity is in the range the groups are small. I load .010" off the lands but have loaded to SAAMI spec OAL and gotten excellent results when I got velocity in that range.
When you find good Sub-MOA factory ammo I suggest you go buy as many boxes as feasible from the same lot #.
The attached picture is my 30-06 firing Hornady SuperFormance 150 gr. SST. A friend gave me (2) full boxes of this ammo as his rifle groups them poorly. The group is off a rest at 100 yards.