I do not know right off hand but I would call Springfield and see if they can tell you. I have seen the XDM 9 and XDM 45 and they are different sizes. I would think the 40 would be more similar to the 9mm.
I ended up selling all 10 of these. A guy bought one, saw I had two (last 2) and made an offer I could not refuse. So, now I am on a mission to get these in 40 and in biotone.