Does ammo quality make a huge difference in accuracy?

[damndave]

At 10 yrds you should be able to put 10 rds within a couple inches with cheap ammo.

Shooting low left means you are anticipating the recoil and pushing as you are squeezing the trigger. Maybe with the quality ammo you shot, you took your time more as the ammo was more expensive? lol

[J-cat]

115 grain bullets shoot to a different point of impact than 147 grain bullets. That could explain the difference in your groups.