Id recommend getting a membership and buying the hulls from the for sale section here.
There is a guy selling hulls on gunbroker for 4$ a pop, they are much cheaper in the Parker for sale section though.
https://www.gunbroker.com/item/964914193
I think the guy on here is selling them for 50 cents a hull. You would probably come out on top joining up and buying the hulls on here.