Re: Precision Reloading For Long Range Hunting by Jerry Teo
My personal method is to use a light charge of pistol powder behind cornmeal filled to the base of the neck. A small piece of paper towel pushed gently into the neck holds this mess in place.
Fire at your rifle range, clean often and voila - fireformed cases. If you are improving a case, this method will get you a 90% formed shoulder, plenty good for the first full pressure loading.
With any fireforming the goal is to ensure the parent case is expanded to fill the chamber dimensions without excessive stretching of the case web. If a case is undersized and a full pressure load fired, the web may stretch to the point where a couple of future firings cause a split.
By careful sizing/matching to the chamber or using a low pressure method like the cornmeal method, the brass can be eased into shape.
Once proper headspace is established and maintained, high pressures can be introduced with little stretching and long case life.