In this Holts Auction review they talk about it. Simon Reinhold says the 22LR killed the rook rifle stone dead and people started boring them out to .410. https://www.youtube.com/watch?v=bfukpZXZE84.Don't get me wrong I wouldn't have a clue. Just going off what he said. There is a beautiful matched pair in original condition at 1hr 12 worth looking at it.