I beleive the inherent lack of gilt edge accuracy in the 5906 lies not with the quality of the barrel but it's fir to the slide. Usually 5906's have a loosely fit barrel.
T squared,
You are correct, barrel fit is extremely important for accuracy in any auto pistol.
The Aussie made RPH Custom barrels are oversize, and definitely gunsmith fit. Add single point cut rifling from .355, .3555, .356, .3565 through to .358 and barrel twist from 1:10 to 1:32. You name it, thats what it will be.