I have not fire formed the 7-30 Waters case, but have plenty of others. I usually use a recommended starting load for the case I am fore forming for. I use as cheap a bullet as I can get and use them for scope sighting, plinking and just general fun shooting until I get them all shot up, then I get serious with load development with the formed cases. I know there are several formulas using Bullseye and corn starch and all kinds of other ways, but I like to shoot and can think of no way better than to shoot at some thing while fire forming. Right now I am having some fun forming up some 22 K Hornet cases. Fortunately I had several hundred 55 grain boat tails given to me, so the bullets were free (a big expense).
BTW - If you buy 38-55 or 375 Winchester cases and form them to 7 -30 Waters, you will not have to fire form. Of course you will need to step down the necks once or twice.
Good Luck and Good Shooting