Sturmtiger (Sturmmorserwagen) made for easy printing at 1/100 scale. The file has the gun barrel at a different angle (on the print plate) than the print in the picture and should print much more cleanly.
If you've never heard of it this is an absolutely insane tank, it is not as I thought a basic mortar, it is a 380mm rocket propelled mortar (both ballistic and rocket propulsion)... this is the closest real word thing I think exists to the 40k Bolter.
The crane on the back is to load the gun, I have the one in the picture glued on a little low because it just looks strange to me at the correct height, but you can assemble it however you like.