In my humble opinion; from owning, shooting, and hunting with double rifles all my life, these are the best overall and in my favorite calibres. Ranked top to bottom.

1. Westley Richards & Co. .318ex, .476ex - Droplocks 1910-Present

2. John Rigby & Co. .400/.350ex, .470ex - Bissel/Rigby Patent Rising Bites

3. James Purdey & Sons .369ex, & .600ex - Beesley Self-Opening bolstered guns

4. Holland & Holland .375ex, .500/.465ex 1990-Present

5. Lebeau-Courally 9.3x74r, & .375ex any era is great here.

*What's your favorite maker and calibre? If different than mine, that's great list it here.