I checked some other resources. Nothing I have goes into any depth about this maker. All list several Barr's in New York City circa 1850...

The census records do not show him. There is a Richard Barr in the 1857 New York City directory at 106 Beekman who is listed as a gunsmith.

http://search.ancestry.com/Browse/view.aspx?dbid=1540&iid=NewYork_NY_1857_059540-0051

Pete