Well I guess that must be the reason they came up with the AOW class. Because I would certainly NOT want to pay $200.00 for anything that didn't go BANG. So from my memory AOW was a $5.00 stamp and covered these oddity type things and pen guns,cane guns etc. But at one time there was a super short 870 pump gun that might have had a 10 or 12" barrel and a 2 round tube. And the company that built them even called them the AOW. And to me that implied it would be a $5.00 stamp. But all the SBR projects I see going on require the normal $200.00 stamp. So what is the difference? Is it because one is a rifle and one a scattergun?Mp5 briefcases are AOWs with the mp5 attached. But I think it differs if it's an MG inside.