Reading Stephen Hamilton's 50th Royal Tank Regiment: A complete history and came across the interesting story of the first Valentine IX 6pdrs and their major design flaw: a lack of coaxial machine gun. Here's how the history outlines the issue and the solution attempted: Not surprisingly this issue was remedied in later marks!
Quite the odd expedient! It is strange - maybe I am missing something - how the first conclusion regarding the 6 pounder was that it was not possible to fit it in the Valentine. Then it was - or did they alter the gun? Then there was no room for a machine gun. Then they found room - how?
"Into the Vally" by Dick Taylor is a good reference for this. In simple steps, before the Mark IX, the Valentine was fitted with a three man two-pounder turret. When the decision was taken to mount the six-pounder, the turret front was redesigned and it reverted to a two man turret to fit the gun, a quick fix so to speak to get six-pounders in action. For the Mark X another redesign of the mantlet took place to mount a BESA coaxial. Essentially a lot of measures taken due to limits to turret size and needing to get something into action sooner rather than later.
I believe the reinstated coax went into a rather lightly-armoured 'cowling', possibly outboard of the trunnion.
Yes, the right side of the mantlet was restructured so what is called an 'armoured cowl' was created to hold the coaxial. It is descibed as producing a 'prominent bulge' on the outside of the turret and being proof only against 7.92 mm point blank (Taylor p45) Here it is on a Mark X. for comparison here's a Mark I with coaxial setup:
Thanks for the reminder to go look at my own copy of Into The Vally. Sometimes I forget what I've read! The reason I asked the question was that in my recent LAC visit, I came across correspondence from Canada to the UK about whether the larger turret would mount the 6-pounder and the answer came back "no": 0502_P1020202 by Seroster posted Jul 23, 2017 at 6:55 PM 0505_P1020201 by Seroster posted Jul 23, 2017 at 6:55 PM
This extract from a report ‘Points of Interest Arising from Operations’ by Brigadier G. W. Richards (23rd Armd Bde) mirrors this account and adds a further criticism of the Mk IX with respect to the provision for smoke. Canadian Military Headquarters, London : T-17842 - Héritage
The correspondence I posted earlier makes me wonder how they got the 6-pounder into a Valentine turret at all...
That turret must have been an unpleasant place to be. From ‘A.F.V. Experimental Progress Report, No.8 – July 1942’: