I'd suggest the max range any rifle is good for is based on the bullet selected, assuming the shooter is capable. After bullet, I look to the altitude I will use it at. For me, the max range is based off the min velocity the bullet is recommended for, with a 5-10% cushion, for broadside shots at the altitude I'll hunt, or 600 yards, which ever is less. Most of the time it is 600 yards. Looking to bullet impact velocity gives me better info than some of the old footpounds rules, in terms of the bullet expanding, creating a decent wound channel, and actually transferring some energy.
So in my opinion, the answer will vary quite a bit, based on bullet selection/altitude. For elk, I lean towards a SD in my bullet of around .260+, which accounts for the quartering shot, so shot angle is not a dominant variable in my calculus... With the advent of ultra LR hunting, there are more bullets available that open at lower velocity than ever before. The bullet my LR rifle likes is rated for a min. of 1,600 fps as I recall. My LR set up is a .280 with a Barnes 145gr. LRX at a MV of over 3,000. The SD is not quite .260, its .257, but the Barnes gives me confidence to penetrate, due to it's construction.
My two cents anyway.