The answer to your first question is, Ryan Cleckner's book on long range shooting. Essentially you need to learn your weapon and be consistent. There are so many factors that have to be recognized and considered based on your goals. Simple answer is fire three rounds at a given distance and see where they hit in relation to your dope card or app. Log that data. This is now your new reference material. Tape it on the stock. Do wind hold offs at 2/3 the distance to the target. You should be able to judge winds with your rifle scope or spotting scope. If your goal is to survive the zombie apocalypse your error window expands. If you want to compete then accuracy is paramount.
Default setting from the factory would probably be around 0 or 100 on the dial I suppose. That's where I start. Rounds typically hit within 4-5 MOA.
Well using a decent ballistic app and getting accurate information for that app is critical for the output to be worth anything. One of my concerns with the above is that if you do a range card in 80 degrees and 50% humidity and you hunt in 20 degree weather, 20% humidity, the difference in performance under those condition variations can make the difference between impact and a miss. Those differences magnify themselves at distance.
First you need to know the G7 Ballistic coefficient of the round you are shooting. Some advertised BC's are a bit optimistic because manufacturers know LD shooters look for high BC projectiles for their reloads. Applied Ballistics has a reference book that now probably now has a newer edition than my 5 year old book, but it had the G7 BC's for many rounds at several distances. Yes according to Brian Litz who actually is a rocket scientist, the BC's change at various distances and his reference book reflects those changes. These BC numbres also go into the baseline bullet profile. Basically wrong BC # bad output from your app.
Next you need to Chrono your rounds that you plan to use for LD. Advertised speeds will most offen differ from what you will get from your weapon because firearms are as unique as fingerprints. The test weapon's barrel may be longer or shorter just as an example of many differences that could affect speed. Once I'm done with my load development, I chrono my rounds with a can if I plan on using that weapon configured that way for LD.
Last you need the environmentals to be entered when you zeroed the weapon and obtained your chrono numbers. You generally put this environmental baseline information into the round profile in your ballistic app. Then when you are shooting under other environmental conditions you put the environments of area of operations environments in the app. The app then should compute the difference in bullet performance under those difference conditions For me and my area in FL temperature and humidity are the biggies for me under 1000yds. I tried to hunt and peck at at corrections on my range cards until until I got the BC Reference book, the Chrono equipment to measure the bullet speed, and the Kestral for environmentals. My range app started to give me really accurate numbers. After that my range dope was spot on and my only issue with not getting impacts at 600-1000 yds was my wind call if mother nature was blowing hard.
Last and I differ from some other shooters in how I adjust for elevation. I use a tree reticle whenever possible. This allows for quick target engagement when that ability is needed. I do not crank the turrets to get my elevation which for me means I just go down for the mils needed for the target distance and over for the estimated wind value. My 6.5CM needs about 8.4 mils. My Vortex Razer FFP EBR2C reticle gets me 10 mils with the tree so no need to touch the turrets. You still need do a similar exercise to what the Video noted above to verity that your scope is not canted to one side or another.
Just My .02
