If a man can shoot a 2 inch group at 200 yards he doesn't have to practice at 400 yards to make that shot. There are plenty of programs that will tell you where you will be at longer ranges accurately enough for elk size game.
There is a lot of BC programs that will tell you "shoulda, coulda, woulda" but that's on paper.
The BC programs wont make you hold your rifle steady, they wont compensate for being winded after climbing a hill at 8000 ft.
The "if you can shoot a 2 inch group you don't have to practice at 400" is back-wards".
You practice a lot at 400 you'll be good to go at 200.
I do a lot of long range shooting, past 1000 yards. Been doing it for about 35+ years in competition.
So I figure I'm good to 300 yards.
Too many things to go wrong at extended ranges, mis calculating wind, switching down range, not taking angles into account, temps etc etc, and that isn't taking account of shooter error when pulling the trigger.
We can all sand bag a rifle to a bench and shoot little bitty groups. But at altitude, after climbing a hill, from leaning against a tree, or kneeling etc etc we'd be lucky to hold 5 MOA.
The vital area of the average elk is about 15 inches. If you're holding 5 MOA, you "should" (and that's a big SHOULD) be good to 300 yards.
Sight your rifle in. Run around a bit, then plop down to a kneeling position, leaning against a tree or something and shoot a 5 shot group at 100 yards and see the size.
If you can constantly do that and hold under 5 MOA, you're a better man then me.
You read all the time about the super long range shots on game. Funny you never hear about the muffed shots, wounded game running off to die a painful death.
Think back, how many "misses" do you read about on the Internet? Who post about gut shooting and loosing a nice elks?