When I was shooting in college my S&W Target pistol hated match ammo. I convinced my coach to allow me to use practice ammo. My match scores improved. We also verified this by shooting off sand bags.
Some years ago one of the major Mags published an article on the effect of cartridge weight on dispersion of 22 long Rifle ammo.
the upshot of the article was that weighing your bullets and batching them in .o2 grain variations of weight caused a significant improvement in group size.