Well, no, I think you were right, Alan. I have seen footage of men swabbing the barrel (I think it removed some of the residue and lengthened the life of the barrel). I'm not 100% that I've seen a German crew doing it - I think I've seen it, but haven't been able to locate it in my collection yet. Definitely seen British gun crews and British tank crews swabbing their guns.
Although I do agree that the sequence shows three guys ramming a round into place, I think the rammer looks rather different to the swab.
Might be wrong; wonder what Strelets had in mind when they were sculpting?
I doubt the chain track would have worked as a kit of parts or rubber belt, perhaps some kind soul will produce an etched set to complete the details on the model... failing that could always add a set of simple plates to the wheels with strips of plastic card joining them not perfectly accurate but should look ok