Accuracy has never been an issue with any Glock I've had, including the G40. I upgraded the barrel for velocity reasons, not accuracy. Every 10mm Glock I've shot with an aftermarket barrel has shown gains of 50-100fps with no exceptions. Literally same load, and up to 100fps gain just by changing the barrel. I changed the barrel to a semi-fit Bar-Sto (had to mill it to fit perfect), Vogel competition Glock trigger, and Tru-glu adjustable night sights.
You have to try various loads or come up with your own magic reload recipe to get top accuracy. Mine easily shoots 1" groups, standing, at 10 yards. Better than any revolver I've ever shot, period.
