Help needed

Currently I'm working on a comparison sheet showing most common AWI guns. I've managed to do French ones and British 3-pdrs. Now the time has come to do British 6-pdr, 12-pdr and 5,5" howitzer.
Unfortunatelly, I can't find any decent scale drawings of these guns, although I know the dimensions of barrels and carriages. If anybody can help me in this matter, please contact me - in my Google profile one can find my e-mail adress. 

Below the comparison chart in progress. All dimensions in centimetres.