Also comfortably from my armchair:

I would go for Rigby - such a classic.

As for .404, most British colonial game department issued their control staffs with .404s and they must have accounted for thousands of eles & buff. How much velocity do you want? Sectional density - I have read that the .404s suffered from poor bullets in its early days, but that was many decades ago. Any modern bullets ahould be up to scratch.