WOW, I have been poking around a little bit regarding maximums with this combination and I saw that the older LEE book suggested a maximum of 7.2 gn. Your load is massive. Can anyone tell me if my Beretta CX4 has a supported enough chamber for even a 7gn load? I read the Glock does not have a supported enough chamber. How about my S&W 1911 9mm?
Chris
Is there a particular reason that you want to do this?
Supermoto did it to make major with a 9mm. Do you just want to do it because it sounds cool? It's a good way to ruin your gun. If you need more gun, get more gun - don't try to make a 9mm something it wasn't designed to be (unless the rules are such that you benefit from doing so).
Have you even tried 'normal' ammo at 100 yards to see how it shoots? You need to establish a baseline, right? How else will you be able to tell if your super-duper ammo is any better?
When you're working your way up, do you know what to look for? Forget flattened primers and brass extruded into the extractor recess - you're likely to get both of those before you come close to Supermoto's load. What particular pressure sign are you going to use to say, "OK. I can't go any higher"? The gun flying apart? Do you think your CX4 is stronger than a 1911?
Also - forget about reloading the brass after you load it that hot.
Good luck. Post pictures of the pieces of your Beretta when you get out of the hospital.
ETA: Isn't the CX4 a straight-blowback action?
Think through how the action works, and what will happen when you use ammo that's much more powerful than what the gun was designed for.