Why make things so difficult. I would let Holland and Holland regulate the rifle for Norma ammo, at same time, I would also stockpile 3 to 4 cases of ammo (1/3 FMJ and 2/3 Soft point). Costs relatively little compared the double rifle. Always nice to have enough ammo so you don't have to worry.

I am a great fan of Woodleigh - works very well for the intended beasts.

Cheers
Johan