Gun testing and giant gun in action.
1st part: a man showing a thing made of different pipes and mounted on a post. CU man loading a cylindrical object into the larger pipe. MS as he bends over by this thing; aims and fires. He repeats this. Then manages to shoot the thing while holding it - looks awkward. Another man is watching. (Both the men and the place have the look of America; but no information).
Now the scene changes to the woods; somewhere in World War One - Western Front ? French artillery unit with huge gun; huge shells. They roll shell onto a cart on wheels which rolls it to the cylinder to load. Man then stuffs in explosive. MS of the men uncovering gun which is hidden under branches; a tarpaulin etc, camouflage. They raise the gun barrel - front diagonal shot.