Someone over at SigTalk has converted a .40 P320 into 10mm by using a .45 FCU in the 9/40 frame and having the .40 barrel chamber reamed.
https://www.sigtalk.com/threads/my-p320-10mm-project.398388/#post-5618028
https://www.sigtalk.com/threads/my-p320-10mm-project.398388/#post-5618028