Gunslinger 4

+1 BAB, +1 Fort, +1 Ref, Bonus Feat: Rapid Reload (Pistol), +1 Wis, +`SP

+2 Craft (Gunsmith), +2 Ride, +1 Perception, +1 Intimidate

Done

Gunslinger 5

Gun training (Pistols), +1 HP

+1 Craft (gunsmith), +1 Handle Animal (Cha), +1 Heal (Wis), +1 Perception, +1 survival

Done

Lars is crafting a Revolver.

Can I take 20 on the craft?

Short answer would be no, you'd be able to take 10, but there is a risk of failure which means you can't take 20.