I have a 284 Win in a ULA Model 20. 55 grains of IMR 4350 and a 140 grain Nosler Partition (I get 3000 fps) has killed many sheep, elk, caribou, and mountain goats out to 500 yards. I got a Kimber Mountain Ascent in 280 Ackley about a year or so ago. After playing around with loads I use 62 grains of H4831 SC and a 140 grain Barnes Triple Shock (I get about 3150 fps). I have used this bullet in many other rifles with good success, only shot an animalope with it this year. The 280 AI is 7 Mag performance for sure hotter than the 284 but in reality the 284 will probably due whatever the 280 Ackley will do in a hunting situation. The 284 Win loaded like I load mine will give you 280 Remington performance. Both fun cartridges. Anyways they are both pretty damn good.
My experience exactly.
The OP didn't specify what game he was pursuing but if for ungulates from elk on down, all cartridges named are good-to-go. With ballistic reticles or turrets now, any ballistic differences between them are meaningless. Practical matters, then, like brass, recoil, cost of build changes would be prioritized if it were me.
Anecdotally, my short action 284 spits out the long TTSXs, the 140s and 150s, at 3000 and 2900 fps respectively with R17. And those are not top end. My last deer with this 284 was a couple of steps south of 500 yds and went to sleep with a single round through the chest using a Zeiss Rapid-Z 600.
