The COW method needs a fast burning pistol powder to work well. You need to play with the ratio to get it just right (Lee dippers work well for this). The more powder you add, the more pressure. The more COW you add, the more pressure. If you start with a certain volume of pistol powder to COW ratio, and need more pressure to case form, add more COW and a little more powder, a little at a time (I'd add more COW, since it's the filler and less expensive). Once you have the right ratio, keep using that ratio. You can put some wax on the top to hold the COW in, but may mix up some if you tilt the rifle horizontal to fire it. Most hold the rifle vertical, and chamber and fire it vertically.