A pretty straightforward question, but it's something I can't really figure out. In Lud, Jake apparently made Tick-Tock the first person he ever shot. A month or two later, when the ka-tet arrives in the Callas, Jake is somehow already a deadly gunslinger.

I was thinking Wind Through the Keyhole would make touch on this or at least acknowledge that Roland was training Jake while they made their way toward End-World, but nope. I guess I can accept that he trained along the way, the way Eddie and Susannah were taught to shoot between the end of Drawing of the Three and the beginning of Waste Lands (or the way Yoda trained Luke to be a Jedi in like ten seconds flat), but it still seems like something's missing.

Was this ever explained in any of the books?