The "b" wing was built to hold a single 20 mm cannon and two .303 mgs in the outboard positions per wing.
The "c" wing was called the universal wing, and could hold two 20 mm cannons in each wing (side by side in the in-board position), or a single 20mm and two .303's in the outboard position, or 4 303s. Plus, the wheels were moved slightly forward on the C wing, and it could hold a 250 lb bomb under each wing.
Easiest way to tell is the "C" wing had the little stub next to the 20mm cannon. The "B" wing had no stub. (if the C wing had only 303s it might be a little harder to tell from the A.... not sure)
Also, I believe (but I ain't got the reference in front of me) that the bulge over the cannon for the C wing was larger to be able to potentially accomodate the dual 20mm load in each wing.
I think the "C" wing was arrived at to allow the units to decide armament in the field.
So the B and the C could hold the same armament.... main difference is the stub and the size of the bulges. (Don't go there....)
(Warning and disclaimer: Now, having said all of this, I must now make the disclaimer for all Spitfire purists that I may certainly be wrong as I am trying to write this from memory based on a few readings of a Spitfire history magazine that I sorta recall, and a brief search of Wikipedia to check my sanity. So if I am wrong I understand going in that I am taking a chance by actually claiming to know much about Spitfires when you get right down to it. )
Jon Bius
AgapeModels.com- Modeling with a Higher purpose
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