I shoot competition rifle and need a bunch of cases, too. I have NO problem using COW and 12-18gr of pistol/shotgun powder. I usually use Red Dot, but almost any of the fast powders work fine.
With my .257 Bob-Imp I usually load .257 loads and shoot, but I am using IMR 4895. With my .270 WinImp and 6.5/06 Imp I usually fireform with COW.
I don't usually go to the matches where they supplement the prizes with Cocoa Puffs, whether or not I like cold cereal, but COW is better hot...if I have any left after fireforming, lol.
Have fun,
Gene

Last edited by Mavrick; 08/18/14.