I believe the date range Tom mentioned goes from 700 to 1300. The latter date may be off (1500? I can find it again tomorrow), but I do remember the earlier date specifically. So any justification for things that are reasonable should demonstrate to have been applicable during that specific time period. No justifications of "The Greeks did it this way in 300AD" or "the Romans had this in 300BC" unless it was still being done by 700 AD. It also means nothing that was invented in 1585, let alone 1985. And even if it occurred in 300 AD and then again in 1800 AD, if it didn't happen during 700-1300, then it's out. So no Roman war chariots.
A lot of BM feudalism or encouraged behaviour fitted more 1500 europe than 1300 or prior. BM's a mix of many things, and isn't true to any one precise historical period or society. Bits and pieces from western european society between 900 and 1500 mostly, I'd say. Borderline 1600 even, perhaps, for some elements.
