[moxie]

As noted in the Berry's FAQ, those bullets are to be crimped using a slight taper crimp. A slight taper crimp is not really a crimp at all. It just removes the "flare" or "belling" from the expander die. Anything beyond that should be reserved for cast bullets with a crimp groove, or jacketed bullets with a cannelure.

The common term for the phenomenon you are trying to prevent is "bullet jump."

You can use those bullets in magnum revolvers with relatively light loads. Powerful but not near "full-house." If you are sizing and expanding correctly, you will have sufficient case mouth tension to prevent bullet jump. That's what's done with 9mm and .45acp pistols all the time.

The crimp in the picture is beyond brutal. It's bullet abuse.

Friendly recommendation #1: Stick with reloading measurements in inches. All American reloading data is built that way. Metric just confuses us.

Friendly recommendation #2: Row out into the Gulf of Finland about 100 yards. Take that Lee FCD and throw it as far as you can. Save yourself a lot of grief.