Everything that I have heard says they are interchangeable. I've read that some of the Knight owners have buying the DPMS mags. But I do not have a SR-25 so I have no first hand knowledge.
I have a T2K SpecTacLr that was shipped with KAC mags. I rescently bought extra mags from DTubb and they are DPMS mags. I had to remove a little material from the front of the mag because the DPMS was a little tight in the magwell but no biggie. So I guess my answer is yes they are interchangable.