1) Conversion between different caliber DE pistols (Mark VII) - Was possible on those, earlier model DE pistols, although this is different and much
simpler on today's models.
Magnum Research Inc. used to sell so called "Conversion Kit"
that contained: Barrel, Recoil springs & rods, Slide, including bolt assembly and finally a magazine. As I have been told by Magnum Research, they don't sell "Conversion Kit" anymore and have only few Mark VII pistols left.
Using an appropriate kit, was possible conversion between .357 & .44, or .44 & .50 AE, I have seen the pictures of those kits.
Also I don't have the information, if it was possible conversion between .357 & .50 AE for Mark VII pistols (asked twice in MR, got 2 different answers, so waiting for more
reliable information on that one ;).
Latest update I have from a friend is this list of conversion kits produced by MRI for .41 magnum in 1993:
- Part # DEP4404 .357 to .41
- Part # DEP4405 .44 to .41
- Part # DEP4406 .41 to .44