Hide that Railway gun ...

 The railway gun needs to be stored way when not being fired, rather than concrete bunker I decided on a simple structure covered in camouflage netting

A basic structure for the netting built from scrap cardboard, with workshop building

A quick spray with some acrylic dark grey paint..

check for fit over the railway gun...

mesh from a laundry bag used for the netting ...

a coat of green paint for the netting with some dabbed on other shades of green; base painted and some dull grass scatter added. Railway gun inside ...

The last scenic item completed, so ready to play the game ...