It seems to me that most Rook Rifles are in non original calibre.
I was told once by an old gun dealer in Bath (now long gone sadly) that when the UK Home office introduced the firearms certificate legislation, many Rook Rifles and Double Rifles where bored out to 410 rather than owners risk them being confiscated etc. Many Rook Rifles were also sleeved to .22rf or 22 Hornet. Back in 1993 he had a whole heap of lovely British Double Rifles all of which had been bored out to 410 and destined for the US.
Rook Rifles tend to be pretty light - 4 to 5lbs, but of the few I have looked at, they balance as a rifle (weight forward) rather than as a shotgun.
Rook Rifles (IMHO) tend to go for a very high price. But if I was looking for a 410 to use as a shotgun, I would either spend $4,000 on a really nice side by side double, that was built as a double shotgun, or to spend a lot less on single barreled 410 British shotgun - we are paying £150 to £200 for a clean one over here, and then spend the rest on something else.
