The new XD-m comes in a .40 with 16 rounds in the mag. Can this be converted to 10mm like many of the other highcap .40s I have seen done with simply reeming the barrel and a new spring?

I don't know, but I would doubt it. Everything I've read on the XDM says that it was specifically built to shoot the 40. If that is truly the case, then the mags are going to be too short to accept the 10mm.

Of course this is just conjecture, as I don't own an XDM, and I haven't been able to find one locally yet to look at.

That's what they have been saying for years about this gun:

http://www.10mmtalk.com/index.php?showtopic=6388

If there is enough handle, you can probably find a way to get a 10mm magazine in the gun and keep the gun fully functional. It's all about determination and checking your facts before you act.
I am not too much of an expert on the XD but my guess is that you probably do have enough handle to convert it to 10mm. It'll probably be a huge project though. Any time you have to enlarge a magazine well, you will have a nightmare of not only sizing issues, but mechanical and fitting changes as well. I had allot of people hyped up on berettaforum.net about building a 10mm Beretta conversion but everyone backed off when I posted a walkthrough on how to do it letting them see how much it really takes.

This post has been edited by brigadier: June 4th 2008 2:47 PM

I picked one up in the shop last week. I would agree that the mag looks to be a .40 and too short to accept the 10mm. What a bummer.