The #4's would be fine in .356 Winchester I'd expect, perhaps as long as top pressures were not attempted - but - they should be checked out thoroughly before hand - what "checking it out entails I do not know. Magna-fluxing was the process in the 70's. Many #5's and #4's have been converted to .308 Winchester & .223 for match shooting over the years. Those rounds run 56,000 to 60,000psi.

I converted one years ago to the .312 Express (Ken Water's name) although I did not know of his conversion at that time. It uses .350 Rem brass necked down to hold the .312 or .313" bullets. It runs 174gr. Hornady's at 2,960fps - about like a .300 WSM.