The tri-pod in the front doesn't make much sense. Unless that is another gun in the background. Can't really tell. Also, I've seen potato cannons that big. It's might be a home made devise for tossing small IEDs or grenades.
It is more like a single barreled 23mm Soviet designed antiaircraft gun.
There are 2 different 23mm calibers, the older WW2 vintage 23x152 used by the Soviet "Flying tanks" tank busters, and the later 23x115 antiaircraft round, also used to great effect in air to air combat. This is likely the 23x115 round.
That front tripod didn't look like it was attached to the gun and appeared to have a LMG mount on top of it.:bs:
I'm with the others, this appears to be some kind of single shot antitank gun shooting a light cannon round. If it was being used in a sniping mode, you'd need optics to actually take advantage of its' range advantage.
I think it's a modulated-pulse, immolator-driven coil activated javelin gun.
The history of this weapon goes back to a garage in Detroit around 1902. Cyrus Evelnutter was experimenting with a winch-jack when the coil let go and fired a tire iron through the brick wall and into a fruit stand out in the street. It was quite a mess -- but anyway ... uh - where was I?