I've shot a lot of Federal seconds, mostly 9mm and .40 S&W. But I acquired quite a few boxes of .375 H & H with 260 grain Nosler Accubonds several years ago which shot very accurately in two of my .375 rifles. I’ve used it for deer hunting here in Wisconsin and for plains game in Namibia. They’ve performed great on deer, black wildebeest, springbuck, and impala.
I did have some trouble with a zebra last year, but not due to the ammo. I shot it broadside at a range of 80 yards, but because of thick brush I had to shoot behind the shoulder and a bit higher than I would have liked. The bullet didn't exit. We didn't do an extensive post mortem, but I suspect it caught just the tops of the lungs. The zebra went about 100 yards with virtually no blood trail, so finding it in the tall grass was difficult. I think a Partition or A-Frame would have worked better, but the Accubond worked as designed.
Overall I’ve been quite pleased with Federal seconds and would use them again on a plains game hunt.