The 400 Corbon is essentially what a 357 Sig/40 cal is to the 45 ACP. The 357 Sig takes the 40 case and necks it down to 9mm. The 400 Corbon takes the 45 ACP and necks it down to 40 cal. The main issue with both of these necked down rounds is making sure you have the correct head space and have a heavy crimp to hold the bullet in place. It can be difficult to reload for and getting the head space correct.
The 400 Corbon duplicates the 10mm Auto performance. IMO, why make the round complicated if the 10mm Auto already does it with a much more simple case. I'd just go 10mm. But the 400 Corbon is a little more wildcat.