Norma oryx is my favorite general purpose bullet. Most of my experience is whitetail with a .338 with them, but have used them in 6.5x55 and .308 as well. Always excellent results. They open up reliably and drive deep.
What velocities are you running in the 156 gr? Have thought about using some in my 7x57.Have only used the 7mm 156 gr and 170 gr Oryx bullets on game with my .275. They work perfectly on whitetail and plains game through sable. The 156 is my go to load. I have not used the 300 in .375 for buffalo.
I’m not sure if you have used the oryx from your 300 WSM since you asked this. I used the 180 gr oryx in Tanzania last year on gazelles, impala, wildebeest, I found it very soft. It doesn’t hold up well to 300 win velocity and bone, but it does hit hard. The skinners supposedly didn’t find them in my wildebeest. We recovered this from an impala at around 100 yards. Also included is a photo of my testing into wet newspaper (bottom bullet). It’s a big difference at range vs on game. I’ve seen very little variation between testing and animals with swift A frame (middle bullet).I’m curious on the comparison between a 180 gr version of an A-Frame vs Oryx with a 300 WSM on the larger PG. The side cut view of the bullets above really show a big difference in design, with the A-Frame’s partition looking like a significant advantage.