First, fill a case to the neck with a fast burning pistol powder. Then weigh the charge and drop 8 to 10 percent of that charge and fill up the rest of the case with COW. I use toilet tissue to seal the neck. Then just fire the load. If the case is not fully formed, add just a bit more powder until the case is right.

This is unnecessary to do with Ackley cartridges, but it is cheaper than firing factory ammo, assuming you have a stash of empty brass. I use this method to form .30 Herrett cases and 7-30 Waters cases from once fired or virgin .30-30 cases.

Last edited by LeonHitchcox; 06/17/18. Reason: added info