Seeing no expert came forward, I started measuring 6prs on various photographs of the Mk IV, Mk V, and Mk V* tanks, as well as various drawings supplied by Bovington.
Surprise, surprise- the dimension does come out at 24" from the muzzle tip to the back face of the vertical gun shield.
This is a pity, as the Emhar gun on its pedestal looks tremendous and the real size looks so insignificant!
I've attached a photo of the three barrels in question from L to R:
Interus - nearly correct apart from the muzzle swell;
Home made - the black ring denotes the position of the i/s face of the vertical gun shield (the rear tapers to give an easier fit); and
Emhar - too long and over-scale diameter.
For anybody else who wants to make these barrels, the following dimensions are given, first in real size, thereafter in 1/35th scale metric and imperial -
Barrel length form tip to i/s face of the shield = 24" = 17,4 mm (0,69");
Wow, that model is great. Is it your work?
May I ask what was your source material for the dimensions and layout?
I am slowly moving along with a scratch built model of a Mk IV and will be 3D printing parts like the gun, so am looking for sources to create the components to make the gun. I am moving forward with the first model at 1/12 scale, but am also planning a 1/6 scale
Misters. Tanks MK-V consisted on armament in Red Army of the Soviet Russia. Also fine instructions and drawings for repair and service of the given tanks have been released. For construction of the given model I used drawings, photos and measurements of tanks and guns made in many places. Look also: