I've used pre 64 M70 300 H&H action to build custom rifles in 300 Weatherby, 300 Win Mag, 7mm Rem Mag,358 STA,and (of course), 375 H&H.
No problems with function at all,and the longer box can be used for more flexible bullet seating with the shorter mags like 300 WM or 7mm RM.
