ImperialFighter said:

I've just noticed in the 3 tops shots I showed on the previous page, that it looks like the whole of the bottom step of the 'chamber' prop is itself 'raised up' a little with an angled bottom section.

Your final 2 shots seem to indicate that much for sure.
It's as if the chamber's base declines inward at the bottom.
Almost makes it seem like a mechanism similar to a car crank.
EDIT: wouldn't that mean that, even with the camera angle being below ground level, the chamber base would definitely be visible in the side shot?