I know we are talking about Glocks, but I was reading this last night, perhaps its the same thing with the glocks

"The CW9 uses a conventionally rifled barrel, instead of the polygonal rifling of other Kahrs. Conventional rifling has lands and grooves that are squarely cut, while polygonal rifling is usually hexagonal and looks more like “hills and valleys,” according to some descriptions. Polygonal rifling yields slightly higher velocities due to a tighter gas seal, but conventional rifling is less likely to build up hard-to-remove lead deposits. Traditional thinking suggests that polygonal rifling yields superior accuracy, but in testing a Kahr Arms P9 side by side with a CW9, the P9 was only good for groups that were 1/4 inch better, on average, from the 25-yard line. "