This is by far the best gallery ever made on the subject of Looper guns. Joseph Gordon-Levitt stars as Joe, a hitman who works in the year 2044 as a "Looper", a specialist in eliminating individuals who have been sent back in time from 2074.
Here is a website in which a prop-maker is creating his own version of this movie prop: Looper Blunderbuss - Finished pics on pg. 13, Moldmaking WIP pics on pg.
The guys ate the Replica Prop Forums are life savers. I think you have the wrong piece of wood.
I started by finding reference material. Looper is a 2012 action/science-fiction film written and directed by Rian Johnson (Star Wars: The Last Jedi). The weapon of choice for these Loopers, as they're called in the movie, is the blunderbuss, a gun that harkens back to the Old West model in name and function. I'll touch more on that a little later, but first let's get started with this blunderbuss! A Blunderbuss does not have a pistol grip.
I fell in love with the look of this gun immediately and vowed "IT WILL BE MINE"!