Quick question: #4 or #43, what's the difference?

[Philward]

RCBS shell holders 4 and 43, what is the real difference between them? Yes 4 is for 7mmRM, 300WM...etc belted mags based on 300H&H and 43 is for WSM cartridges. Any functional difference for seating primers with a hand primer? I think I measured a .003" difference from top of holder to base where case head sits.