Trigger control, grip, stance. That is where your groups are.
Exactly! 90% of us aren't capable of holding well enough to take advantage of the inherent accuracy of our pistols. I really happy to shoot under 4" groups with my Glocks (25yds). Changing barrels, or anything else for that matter, is not going to make a Glock into a target pistol. If you're changing the barrel for the tighter chamber/better case support, or lead capability, it's worth it. Otherwise spend your money on ammo and practice.
Savage