closest thing I could find to a lever action was this falling block.....
http://www.thefirearmblog.com/blog/2010/09/14/an-esqusit-beautiful-and-steampunk-esque-50-bmg-rifle/
http://www.thefirearmblog.com/blog/2010/09/14/an-esqusit-beautiful-and-steampunk-esque-50-bmg-rifle/