Ducmarc, as you would know I like a .450 NE with 480 gr projectiles for bovines in general. My only cape buffalo was taken with a .375 with 300 grs bullets.

I do want to use my 10-bore on water buffalo one day. It should prove adequate with proper projectiles.

What I would go for.

1. A used NE double such as Merkel, Chapuis or similar in .470 NE or .450/400 or similar. Should be able to find one for less than 12K unless things have changed a lot. (?)

2. If black powder.

I would not go below a .500 BP. A 12-bore DR or larger would be better. In the BP days the .450 BP and .500 BP were really medium game rifles. A good careful shot and placement with an adequate projectile will kill a buffalo no problem. You will have a PH to shoot it for you and drop it if there is a problem with a lesser rifle, if there is problems.

My BP experience is only armchair. So at that value only.