Good accurate ammunition is the most fundamental aspect in target shooting. Without it, spending time on training, equipment or other factors is a waste. If you are not confident that the shots you fired will hold an acceptable group on the target, then making adjustments to your equipment setup, or your position will be a fruitless exercise, since you could be making adjustments to fix a non-existent problem.
This article which was originally published in Smallbore Australia, details how a variety of target .22 ammunition was tested and the results.