I disagree. A moose presents a big enough target to justify such a shot with a 4 minute rifle. The man who can shoot up to his 4 minute rifle at 500 yards, on demand, under field conditions would have little trouble killing a moose at 500 yards. But if he can't, having a half minute rifle would be of no benefit to him because he couldn't hit the moose with that either. Big game is not killed by firing groups, and even a 4 minute rifle is will put its first round well within that 20" circle.
My OCD side hates it, but theoretically very true!

500 yards at 4 minutes is (give or take) a 20 inch group and more importantly 10 inches from point of aim....A dead moose will be the result.
My buddy's wife (she shoots with us) shot a Boone and Crockett class speed goat at just under 450 yards. The rifle was a 4 minute 30-06..... 4 minutes, but the cold clean shot was always dead on.
At the shot the guide was so shocked (she hit and stoned it) he dropped and smashed his binoculars on the only rock around....That is how its done!
I believe if we want the privilege of shooting game at long range we owe it to the game to bring our very best effort. I spare no effort with best quality equipment and practice relentlessly in this belief.
Even then there are many times I will not touch the trigger.
Minute of angle is plenty of accuracy for the 500 yard shot.
Sadly the first time a new long range shooter tries his "minute of angle" hunting rifle at 500 yards it wont look like a damn bit like minute of angle.
The idea of buying an accurate rifle then being able to hit game at 500 yards is pure bullsh1t...It isn't the rifle that makes the shot.
The worlds best equipment will never tell you when not to shoot.
The best (and only) bet is to first shoot a few thousand rounds at long range. An average moa capable rifle will do.