First: I clean my locks after EVERY shoot. I have Never pulled one of My locks and found it rusty or even black and cruddy.
With that said; a friend gave me one of his rifles to clean, been shooting for maybe 4 or 5 years, ONLY shot blanks (Civil War Reenactments), and when I asked what oil he uses he replied "What's that?".
He had never pulled the lock, he didn't even know it could be done.
The following photos are not really that clear but if you zoom in you can see the rust, just surface rust luckily.
I just soaked it in a mixture of Ballistol and Break Free (because that is all I had) for a couple hours while I worked on the barrel (also had rust, and Lots of crud) and had lunch.
Then I went at it with a brush, rinsed in water, flushed with alcohol, and then a goodly amount of Baricaid Oil and let sit overnight. Then wiped off the oil and reassembled.
(you really have to zoom in on photos, it was much worse then they show).