I think wizardofflight has got the basic measurements of a ANH DH-17 down in his blueprint , obviously measured from a MR Rebel Blaster replica, which had been based on measurements from a Sterling machine gun.
The actual props used in ANH and ESB were casts, and there was some noticeable shrinkage in the casting process though. The scope rail and side greeblie are also wrong in MR's replica - and therefore in this blueprint too.