I'm about to start loading for an upcoming safari, and I've not loaded for 375 H&H before. Is this a round that absolutely needs a crimp? The bullets are 260 grain Accubond, and they do have a cannelure.
No, not absolutely.
Any recommendations in this regard? If so, can I achieve the crimp with a Forster Ultra seating die, or do I need a separate die? I've not previously handloaded rounds that required crimping.
Use a Lee Crimp die and crimp at the cannelure. Better yet, find a safe, accurate load that fills the case to just below the bullet base with the cannelure at case mouth.
