I'm not a photographer myself, but here are a few pics of a camera mount that I just made for someone else.
It is meant to fit the 28 mm diameter barrel of Rob Allen or other rail guns, and I tried to keep it as clean as possible on the outside and bottom where the shooting line would be. The aluminum piece can be adjusted for the desired height with the range of pre-drilled holes, or even flipped upside down if desired to get the camera up above the gun. The clamping knobs need only be loosened, and not completely removed, to install or remove the mount. And lastly, the knob that screws into the camera base is captive, so it won't fall out even without the camera attached. The clamping assembly is Delrin, so as not to mar the gun, and the camera arm is aluminum with a neoprene rubber pad.
As alway, any and all constructive criticism is welcome!