Hi Alden,
I have the same rifle in the same caliber (50), probably as they were being phased out.
I think I got mine through Cabelas a few years back. The twist listed as 1:48 for this 50 caliber, if I recall right, while the currently offered Pedersoli Missouri rifle in 50 has a faster twist.
I, too, wanted to stay with 50 caliber (had the gear already for that caliber), and the slightly shorter barrel length is better for me as well.
These kinda look like #9 in the above pictures; pretty cool!
How does yours shoot? I've been trying to come up with an accurate load and while it's getting better (I've probably got just under 100 rounds through it), it's definitely no one hole wonder.