I used the 7 RM to take most of my game at ranges beyond 400 yards, some over 500 yards, for years. The velocity was 3125 fps in 3 different rifles, just a velocity I settled on for prone shooting and comfortable recoil.
I always wanted a 280 Ackley because it would accomplish the above and was an excuse for one more rifle to play with. I know that particular combo of RL 22 and 140 Nosler BT's was deadly accurate from the 7 RM and the same velocity from a 280 Ackley would be the same, given the same twist.
Any excuse for more rifles to enjoy and experiment with and improve knowledge and marksmanship and take game cleanly or make better scores, whether it's 45-70 or a 257, is "good" for those of us who enjoy rifles and reloading.
I could buy a dozen 30-06's and have bought about 8 and yet I have to try 150's, 165', and 180's with several propellants over several range trips in each and every one, though it's been done by hundreds of thousands of people before in the 30-06.
It's just that my last 300 WSM shoots 3 different types of factory ammo into the .3's and .4's for about any size game and I am wondering why I reload right now at all, except 180 Federal Accubonds are $54 now for 20 rounds.
Uh...yes, the 280 Ackley would be great if it pleases you and that's the only person you need to satisfy. I personally think the extra 125 fps to 175 fps, depending on the barrel, over a regular 280 is worth it to me, though MD would disagree. I just know I'd nick the hair on the belly with a 280 while a 280 Ackley would pop the heart. Sometimes it's the inches that do count.