Bruce, you have way more experience in moose country and with load development than I do, and I respect that....
That being said, "accuracy" is a relative term..... OP spoke of a potential 500 yard shot.... Let's say the DRT zone in a moose is about the size of a basketball... 10 inches..... If your rifle (and you for that matter) shoots 2 MOA then you are potentially looking to use up that ten inches at that distance.... This on top of wind drift and drop compensation....
Of course, 500 yards is not your average moose shot, but taking OP at face value, the majority of advice was offered accordingly.....
You sure must have small moose in Ontario!
I would say the deadly zone on a mature moose is about twenty inches, considering the big deadly spine and hump area on a high shot, it may be more.
The OP said super accuracy, usually meaning sub MOA. So what's the point in having a rifle that accurate, when taken to the hunting field where it would be an extremely rare shooter who can shoot two MOA and a more realistic figure for moose hunters under actual hunting conditions is probably more like 4 to 6 inches like at 100 yards, even with your run of the mill rests, like resting the rifle against a tree and the shooter is well practiced.
Besides the poor shooting at game that I have seen, I base part of my opinion on the results of a major shooting competition that ran for several years in BC and Alberta, starting in the early 1970s and may still be held in some areas, the Rifleman's Rodeo.
It was designed for hunters, using life size big game animal targets with scoring rings place over the vital areas, with the ten ring being 4 inches and going down at least an inch between each ring of 9,8,7 and so on. The targets were from 100 to 300 yards, with running, actually smoothly running on tracks, deer and antelope, at 100 yards, a bear at 200, a sheep at 250 and a goat at 300.
A shooter could use any position, like prone or sitting, but could not rest the rifle on any inert object and was allowed one shot at each target. When he/she was ready a target would appear, but the shooter would not know which target until it appeared. The stationary targets would pop up and stay for 4 seconds.
I was one of the club officials running the show at our town, I was secretary of the club for several years and I still have most of the official scoring books.
A perfect score would be 50, meaning each shot in a ten ring. There were several hundred events shot every year and in the 8 or 9 years our club hosted the shoot, and shooters came from wide areas in Alberta, BC, and, even one or two from Sask., the highest score ever shot was 44 and this by a young lady who's dad, that always shot in the events, was a virtual professional rifle shot.
More years than not there wouldn't be one single score of 40 or more, shot! Meaning no one would average all five shots in the 8 ring, for those years. The Rifleman's Rodeo, which started in Calgary, was designed to get hunters out shooting and meant to attract hunters, as well as target shooters. The rifles had to be at least 6mm bore.
And here was the pay off. Many, and I mean a lot, and often, shooters who were hunters, but not target shooters, would shoot their five shots and not touch a scoring ring, not even a 1 or 2 ring. A score of zilch!
As I stated, I still have the official score books from several years of shooting, so I am not going by memory, but have the books to prove what I have said.