Mostly because it doesn't actually shoot anything. It's just a life-size replica. One that brings the N7 Valiant sniper rifle out of the game series and into the real world.
The bulk of the rifle is molded, with a few parts carved from wood.
This isn't the first rifle props builder Zander Brandt has constructed from the Mass Effect universe, but like all good craftsmen he just keeps getting better the longer he's at it.
You can read all about how Zander built it at his worklog below.