When I was a kid, Dad decided to build a .40 cal caplock. Golden Age Arms had their shop downtown from where I lived, and he got lock, Douglas barrel and some parts from Jim Johnston. I borrowed some other parts and sand cast the trigger guard and buttplate. It took about 2 years of evening and some weekend work, and was finished in 1970 when I graduated from High School.
I think it took Dad longer to fit the sights than any other task, and first trip to the range, he had it sighted in to take the center out of a pie tin at 100 yards. He could hit whatever he could see. I fired it a few times long ago, and have it today - hasn't been fired for several decades, and the right day will come soon.
My first rifle was a .54 cal. Gallagher, and I began casting for it even before firing the first round. Naturally my flint preference runs towards the .54 cal, but I also shoot .50 cal in flint and percussion.