Ive been fire forming with cornmeal and cream o wheat for many years with no signs of bbl wear at all. In some pretty good bench rifles as well.
I also have built a fireforming platform for making 338-408 (338 snipe-tac) cases for my customers. Im using 40grns of WC846, cream of wheat, toilet paper= 95% form. I just use any fast burning cheap powder, it all works.
I used an old test reciever i built years ago, it has a 18" bbl, all mounted on a steel u channel, it can be bolted to a bench or just set on a block of wood, i pretty much rapid fire, as fast as i can load it i shoot. When your forming hundreds at a time its the best method. I dont have to worry about cleaning or the bbl heating up.
As many as you will be doing i wouldnt worry about the bbl at all, just keep it clean while forming the brass. I run a patch through after two shots, clean after 10. Just what i do.