For me, the primary purpose of a double rifle is to shoot elephant. Therefore penetration is a very serious concern.

I would use a .577 x 2 3/4" on buffalo with good quality solids if I could choose my shot carefully. However, 1650 fps is quite marginal velocity to achieve good penetration, especially when pushing a bullet with a large cross sectional area, and with a sectional density below 0.300.

It would be a lot of fun to use a .577 x 2 3/4" on plains game such as zebra, kudu, eland and giraffe. On lion and leopard, I am sure it could kill quite effectively. However, I suspect there would be times when this cartridge would be less than optimal for elephant, hippo, buffalo and rhino because of the penetration needed on those animals. Consequently, the value of .577 x 2 3/4" vintage rifles is typically a quarter to a third that of a 577 x 3" of the same maker in equivalent condition.