The truth is that most of what are considered "classic" cartridges are very hard to improve on. My votes:
# 1. 30-06 Springfield, its been around for over 100yrs, and is still the standard most new rounds try to compare with for all around use.
# 2. 375 Holland & Holland, , once again its been with us for over 100yrs and it too is hard to improve on for big game
# 3. 7x57 Mauser ( 275 Rigby) , it's also been here for over 100yrs and still does great on light to medium game.
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