I now have a fairly new Springfield R O 9mm compact. Is it possible to convert this pistol from 9mm to 38 super? Is it as easy as a barrel and magazine changes?
In a word: Yes.
Folks have used Colt 38 Super mags and I think EFK makes a semi drop-in barrel for 1911.
The compact might be finicky for a while till you get the right extractor tension and magazines right.