It does look staged and the gun is mounted on the "Sokolov" mount, (note the wheels), rather than the typical pressed steel "sled mount".
David is right that the muzzle booster is missing and would normally be in place to both center the barrel in its travel and create backpressure to help reliability, (Maxims CAN be fired without the booster, but it is a sloppy exercise and will eventually lead to water jacket leaks, as the bouncing around of the barrel breaks down the asbestos twine, which helps seal the forward end of the water jacket).
Here are some nice pics of a Maxim 08 in correct, battlefront regalia.....
http://www.militaryfactory.com/image...urrentPic=pic1