As far as I can tell, parts for the slide, including barrel and slide are the same product for 3913 and the 6906.

I have both and have been trying for years to decide which is the better of the two for my uses. Maybe in a couple of more years I will have arrived at a definitive conclusion. Until then, more and more field testing.

Until conclusion of this rigorous testing, I am carrying a very scuffed up and well used 908 as a daily carry gun. Sometimes I succumb to dark forces and carry one of my Austrian imports.