From the SRD page for Gulch Gunner:
A gulch gunner adds Disable Device, Escape Artist, and Knowledge (dungeoneering) to her list of class skills and removes Knowledge (local), Ride, and Swim from her list of class skills.
When selecting Gulch Gunner, the former three listed skills are gained as expected. However, the latter three are not lost, and remain listed as class skills.
Oh geez, bug yes, and a dangerous fix to boot. Gunslinger never was set up for Class Skill removal. This will be involved, and I'm already passing out.
Hmm, apparently I'm wrong. I did set this up, never finished it though.