I've been workin' on the same one for two summers now. I only get to work on it in between school semesters (summer and a few weeks in the winter).
I started with a plank (an honest to God rectangular plank) and a barrel drilled for a breech plug but not included with the barrel.
I'm not in a hurry or anything, it's kind of a way for me to take my mind off of the real stuff I'm supposed to be doing. Plus, I have no idea what I'm doing, so everything takes longer than it should.
I currently have the lock, barrel, triggers, trigger guard, and butt plate inlet and screwed down. I was in the process of removing the extra wood and installing the patchbox, before school started up again. When summer comes around again, I should be able to rough out the majority of what's left.
In all, I'm planning about two and a half years worth of summers and winters. The next one will be faster of course, but like I said. I'm not in a hurry.