Gaijin has actually modelled these incorrectly. These aren’t mounting plates, just temporary covers for the same rail system used on Challenger 1. These same blocks are visible on CR1 turrets during assembly:
Regardless the make up of the composite is just visual, gaijin does not generally rely on the internal make-up for NATO tanks were the details are sparse. They just set the overall protection figure. The CR2 program requirement was actually only 350mm KE on the hull, 500mm KE on the turret. The claim for 500mm on the hull is from that old document during Challenger 1 development that talks about Challenger II and III.
I mean, to be fair- which year is that requirement document from? It strikes me as odd that their only requirement figure was, literally; “just don’t make CR2’s armor worse than CR1’s”. And even if that was the case, I find doubtful that they would carry on CR2’s production with just the same protection levels as CR1.
Likely 1990, as they are still considering upgrading the CR1 fleet with an MLI at the time. There are a few interesting images that have surfaced recently from a Kew archive document about the CR1 MLI proposals, though there is nothing specific on final CR2 protection levels
This is another interesting one that details the hull front protection of CR1 (listed as lower glacis, but this is what we would call the UFP). Existing CR1 at 300mm, Gulf War CR1 at 350mm (spaced applique plate), proposed CR1 upgrade with dorchester still at 350mm (maybe without the applique?).
Point being, there isn’t a solid claim to the 500mm figure that I have seen, it just gets passed around often enough that people assume it is true.
It is assumed dorchester is a different arrangement, though many people often refer to chobham still and the differences between them are unknown - often dorchester is used to refer to the entire armour system, not specific pieces. I suggested the difference might be that CR2 achieves 350 without use of the applique plate, but really not enough is known. The turret achieves a higher KE protection by making the casting much heavier (can’t find my images for this at the moment).
It was originally assumed these were mounting blocks because no one knew better. Images of CR1 exist with rails, and now also images are seen with covers over the rails.
If the discovery of these images were reversed (Cr1 rails → Cr1 covers → Cr2 “plates”), no one would assume the CR2 uses plates.
This is sorta my point. People assume dorchester is a distinct composite design (vs chobham). The term only seems to have come to life when CR2 was presented, otherwise the armour is usually referred to as improved chobham. This creates a possible illusion that everything changed, when it’s very possible some things didn’t (hull armour).
