Lately, I'd have to agree that there is no better advertising to a would-be criminal than a weapon in the back window. They're stealing police weapons now out of squad cars, why would they leave my personal vehiclealone?

Aside from that, what better way to thump, rumble,and bang your firearms around. Yes, some are made for it (like ARs with iron sights), but I think you'd have to ask yourself what might be served by carrying a scoped rifle that way?