It's never occurred to me to change the barrel on a pistol unless for a threaded version. Are aftermarket barrels more accurate? What's the benefit?
I always here how Glock is the best, but always here of people replacing the barrels. I never here of people replacing the barrels on a Sig unless it's for threaded.
I can't see a barrel making any semi auto noticeably more accurate. I will say I am a much better shot with my Kimber 1911 than my Sig P226, but that's a lot to do with the triggers.
I have also never shot my pistols from a bench, only standing. That being said, my 8-10" group at 25 yards has been enough for me to pass regular pistol quals every year.
I guess I don't see the need or understand why so many people want to change barrels.