Vehicle design and service history:
After the prototype was tested in the middle of 1940, the Mark I was promptly put into production. Though none were ready for the French campaign, they were later sent to Egypt and fought the Italian invasion in the war’s opening stages. The Crusader was designed to maximise interior capacity, with the big sloping turret, with its iconic flat hatch with the telescope situated within it instead of a cupola.
The 40mm of armour was made to withstand the majority of tanks, which were equipped with 37mm guns at the time. Sand guards were fitted to early production vehicles, mainly to cover the back portion of the tank. The 6th Royal Tank Regiment of the 7th Armoured Brigade was the first regiment to engage in combat with these brand-new Crusaders Mark I’s. They used their speed as a screening technique while fighting alongside Matilda infantry tanks.
With the introduction of the 50mm armed Panzer III’s additional armour was needed. This lead to the Crusader Mk. II, and then eventually later improvements in production that added further protection. With the tank shortage now well and truly over it was time to begin mounting the new 6-Pdr gun, in which the Crusader was the first tank to receive this weapon. Initially the Crusader Mk. III received the L/43 6-Pdr Mk. III, but later production models began seeing the L/50 6-Pdr Mk. V with better performance.
Role in-game:
The main difference between this Crusader and the Mk. III already implemented in-game is simple. This Crusader Mk. III has the extra armour pieces of 14mm thick armour welded to the nose, front glacis, and front plate. As well as the better 6-Pdr Mk. V L/50.
Another point to consider is that this tank was also used by the French and could be a vehicle in their tree.
In regards to the APDS round performance, it would have the characteristics as mentioned by @commissarcarl in his post about the Churchill Mk IV, where they posted the following data about the APDS:
Pictures of data for the 6pdr APDS
Chart of penetration of different British ammuntion at an angle of 30 degrees
Realistically any 6-Pdr could fire APCR and APDS ammo. Though I’d personally limit it to 6-Pdr Mk. V and M1 57mm guns, as 6-Pdr Mk. III tanks were all replaced by the time APCR and APDS entered service.
Probably the smartest idea to, also that would be a reason to justify having a second Crusader Mk III, and at the same time it would be easier to balance them, since the two Crusader Mk III would have seperate BR’s.
Of the vehicles that is either using the 6-Pdr Mk. V or the M1 57mm, then the Churchill III & German Churchill, could really use the love of having the extra penetration of the APDS.
Where most of the vehicles using the 6-Pdr Mk. III, have mobility to get on the flank of the enemies.
Issue with the Churchill Mk. III in-game is that the vehicle model is actually based on a Mk. III 6-Pdr tank, not a Mk. V 6-Pdr tank. I’ve reported it, so one day it’ll get fixed.
What we have.
What it should be. This is a Churchill Mk. IV, but I’m purely referring to the gun.