I wouldnt use corn meal... A friend of mine was fireforming brass for a 22-250 AI that way using cornmeal and 13 grains unique. I really wasnt sure about it and didnt have a good feeling, I convince him to tie a string to the trigger and set the rifle on one side of a tree with us on the otherside and fire it where we would be aways from it. luckily for him he listened. The pieces of the gun we managed to find, they now all fit in a shoe box. the bell of the scope was found about 100 feet behind us. for fire forming I seriously recommend just using a parent cartridge. but if ya truly must fire form a case I recommend looking through Varmint Al's reloading page before you proceed. http://www.varmintal.com/arelo.htm#Forming_22_250_Brass