Sure. We use a punch and backing die combination. The punch is a hardened piece of carbide the diameter the flash hole needs to be. For large rifle, .080". For our small rifle, .060". The backing stem, which is also carbide to hold its' edge, is inserted into the mouth of the casing and contacts the inside of the bottom of the casing. The casing is then driven, by the backing stem, onto an alignment guide which contains the carbide punch. The way we have improved the punching operation since Larry received his casings, is by designing a more accurate guide bushing, that the casing is pushed on to, so the flash hole is more centered in the primer pocket. Before the new upgrade, from time to time you could get a casing with a flash hole out of center by about .000" - .015". Since the improvement we are now about .000 - .004"
If I'm reading this right the backing stem would have a hole in the middle to accommodate the punched out brass bit and the tip of the punch as it comes through. The improvement of the guide bushing allowing for better control of the hole location would then allow for a smaller diameter hole in the backing stem. This in turn would lead to a cleaner edged hole and less dishing of the bottom of the primer side of the primer pocket.
Am I on track here?
Correct. But, there is a ratio you need to follow during the punching operation. If you close the gap between the punch and the backing die too close, you will actually create a burr on the inside of the casing. If you take a look at Lapua casings, they tend to run the punch a little too close to the backing stem, as a lot of their casings have a slight burr on the inside. However, their flash holes appear from the outside to be very crisp. Not saying anything bad about Lapua or how they make their casings, it is just an observation I have made. When you punch any metal, there is a shear zone and a tear zone. When the punch first contact the metal, the punch cuts into the metal sharply. As the punch continues through the metal, pressure builds up. When the pressure the punch is creating by pushing and cutting the metal overcomes the strength of the remaining metal, the metal tears out. This tear out is what prevents a burr on the inside of the casing. Here is a link to a better explanation with pictures. Punching Diagram
