What is your recommendation for the best load for .416 Rigby in a a CZ 550, assuming Cape buffalo is the primary goal, but other, smaller game are also on license?

I've been using 94g of H4350 with a 400 grain TSX.

Sub MOA, temp stable, and fairly available.

That load works well in my Dakota and my Ruger.

I have been using 95 grains of IMR 4831 with a 400 grn tsx
With good results. In my cz 550 . Also using same powder at 98 grns with 350 grn tsx.

I took a slightly different approach. 350gr Barnes X propelled by 98 grains of AA4350.

From my 550 Safari Mag rifle is sub MOA at 2680 fps. Recoil is moderate.

Have taken Cape Buffalo, Gemsboc, Hartebeast, Bison, and piggies with that load.

One shot on a wounded Buff laying down in the grass hit his right thigh, broke the femur, went entirely through the barrel and was found under the skin at the front of the chest. Penetration of way over 6 feet. Front of bullet was blown off.

NE,

My rifle is Ruger M77 Express. The load is in Norma brass, Federal 215 primer, the charge is 101.0 grains of IMR 7828SSC under a 400 grains Swift A-Frame clocking at 2440 fps and shoots into 1.0 inches for 3 shots at 100 yards repeatedly. Took two buffalo with the standard shoulder shots at an average of 40-50 yards, one shot each. Recovered one bullet and it was a classic A-Frame mushroom.

I am also experimenting with one of the new IMR Enduron powders, IMR 7977, which is more temperature stable and has proven to be excellent in my 470 Nitro. Clean burning and lower pressure.

From the IMR Web site

Powder IMR 7977
.416" 400 grain bullet
COAL = 3.700"
Start 108.7 grains 2,391fps 40,000 CUP
Maximum 114.5 grains comperessed 2,510 fps 43,900 CUP

Good luck

I run 410gr Woodleigh RNSN on top of 104gr of RE22 for 2530fps in my CZ550.

Cheers.