I agree with the conclusion that it is ash. It looks to be a parts-gun to me. The lack of a ramrod and the hook thingy up on the fore-end suggest that it is a punt gun of sorts, used for water fowl hunting. The gun is loaded and laid across the gunwale of a boat and fired as if it was a cannon at ducks setting on the water.
When I was a boy I saw some old antique guns like that in the sport shops along the Hudson River. Some flint and some cap-lock. Collectors have bought them all up now.
Best Regards,
JMC