Thanks Phillip, I will speak with my local bearing shop early next week.
I tried a couple of CMP wheel nuts on the gun hub but they didn't fit. Felt like they would cross thread if I pushed them any further than the half turn I coul move them by hand. I'll try a few more nuts.
http://www.ebay.com.au/itm/1-6-Giant...oAAOSwc1FXYZtS
Mike, there is a 1:6 Sherman on ebay now. Made of fibreglass and with petrol/gas engine. Price is $1900AUD. Quite heavy, and too large to be easily manhandled into back of the car. At least I can pick up the 1:16 ones. Also seen an assembled Armortek 25pr gun on ebay recently. Starting price was initially £800, but after a couple of weeks without selling......the price went UP to £850!!!!!! A stroke of marketing genius. Dont know if it eventually sold, but now I see another one up for sale. Definately NOT same gun, because this one is a kit requiring assembly, whereas the first one was already built.
I would love an Armortek tank, but $$$ and shipping weight make than an impossible scenario.