I know zero about the XDM, I'm a glock guy. But I was recently looking at getting an xdm in 5.25. I was looking at the frames of the 5.25, 4 and 3 and they all look very similar. Is there any way you can take the slide off the 5.25 and add a complete 4 inch or other slide and it will work?

I've asked around and from what I've gathered, they don't offer complete uppers. I have an XDM 4.5 and would love a 5.25 slide..

I don't think you will get a new slide stripped or otherwise. Don't think you'll get a new frame either.
Aside from complete guns I don't think Springfield wants these components out there at all.
Why do I think that?...
I broke my 5.25 slide. I was sure S/A would not fix nor replace it under warranty so I asked them if I could just buy a new slide. They said "no" we don"t sell XDM slides. They offered to take a look and asses my gun if I would send the complete pistol to them and they would pay for shipping both ways. I did and in 9 days I had my 5.25 XDm back with a new unserial numbered slide.
 While Springfield had my gun I bought another 5.25. This allowed me swap slides & barrels from one 5.25 to another 5.25 and I found they fit perfectly and ran great.
I have since sold the extra 5.25.

I wonder if anyone out there has purchased a new XD/XDm slide or frame?

Hope this helps
VonBark

 

Several months ago I saw a 9mm complete upper offered on GB. It lingered for several months.

I saw another one here briefly.

What is assess?

Several months ago I saw a 9mm complete upper offered on GB. It lingered for several months.

I saw another one here briefly.

What is assess?

Yes. You can swap slides on the XDM frame.

I have a 5.25 XDM in 40 and my best friend has a 4.5 in 40 and we swapped slides so he could try my frame (with PRP Extreme trigger, Extended mag release and grip  safety) and I sold him on getting the parts for his XDM