Can anybody confirm the diameter of the early type cooling jacket (slots instead of holes) on the .30 cal Brownings mounted in the wings of the AVG's Hawk 81's? I found the attached drawing -- when scaled for the 1/8th scale model I'm working on, the resulting 0.25" diameter barrels look large as compared to photos. This made me wonder if aircraft MG's may have had a different cooling jacket of smaller diameter. It might just be an optical illusion.