A couple of things I can add. First, make sure you have a consistent rifle. Doesn't need to be a super BR rig but you must have the confidence that in ideal location, you would know where the bullet will arrive. I feel 1/2MOA is a good min. for a shooter at LR, MOA is max.
Test at different ranges to ensure that the load continues to do what you predict. No use trying to compensate a few inches with a load/rifle that can't hold 1 ft at that distance. Watch changes to your load caused by temp.
Then there is the optics. Some scopes just let you see mirage better then others. I have a Pentax Lightseeker 30. Certainly not the best optics in the world but man can you see mirage. Target image is still very clear. Really helps with doping.
Conversely, my Elite 4200 scopes are crystal clear with better resolution. Mirage does not show up as well even with AO is off focus.
Don't know if this is a coating issue or whatever but the Pentax will be on my LR target /hunting rifles when possible.
Test the consistency of your equipment - critical to your success. At 400 to 500yds, set up a target like a clay pigeon. Watch the conditions take a shot. Odds are there is a miss. Spot the impact and shoot again without moving the sights. Does it hit in the same spot? Repeat until you are confident that the bullets are landing in the same spot. Then adjust and see what happens.
If the POI covers a large area (many times larger then the intended target, hits all over the place), then you know that the rifle/load/shooter is not suitable for that distance/target. Be honest with yourself and change what needs to be to get you shooting consistently/accurately.
I imagine a disc the group size of my rifle when compensating for wind/conditions. I want the highest probability that a bullet falling into this area will engage the target. With small targets, the area of fire will be bigger then the target so there will always be a chance of missing no matter how well I dope.
If I expect the bullet to land on top of each other, I would get quickly demoralized because you just can't dope precise enough. The rifle will not let you. Understand the limits of your equipment AND the task you are presenting yourself.
To simplify, let's say your consistent group size at some long distance is 8 inches for 5 rds under ideal conditions. You are trying to hit a PD which offers you a 3"X8" target. Right away, I know that perfect shooting will only give a hit 50% of the time, maybe a bit less depending on how you do your math. That doesn't mean you accept missing 50% of the time but if your bullet lands within a few inches of the PD (within that 8" circle), you know that you have a 'hit'.
You just have to direct that area of fire over your target so that you increase the probability of a hit. With a bit of luck, you connect.
Why I laugh about PD shooting at extreme distances. It is a lot of fun, yes but call it intended shooting, no. When the target is less then 5% of the group size of a rifle, this falls into spray and pray. With enough bullets, anyone can hit anything at any range. That's not what LR hunting is about.
The target area and the accuracy of the rifle/shooter under the conditions presented must be such that a probability of a hit exceeds 95%. Otherwise, get closer, don't shoot.
So that 8" area of fire on a deer giving a kill zone 12X12 leads to a 100% probability of a hit. Now your skill to compensate for wind matters because you know the bullet will fall within an area suitable to take out the target if you can dope appropriately.
Get out there and burn lots of powder. Be very systematic and watch your variables. Don't get that barrel hot as this really throws a wrench in the works. Consistency and repeatability is what leads to accuracy.
When you know that, you are well on your way to being a great shot.
Jerry
PS Alot of LR hunters will use the spotting shot before engaging the game. Just gets rid of all those variables at LR.