I had a good friend who had a 45cal smokeless built that took a brass cartridge to hold a large rifle primer and he hated the thing. He really struggled to get a good fit with the brass.
I personally prefer the 209 primer system.
If you are looking for parts for a build check out Arrowhead Sporting Goods LLC
That is where I bought almost all of the parts for my new 45.
You won't have as long of a wait to get a barrel.