It's a common thing, and the answer is both more complex and simpler than it seems.
First thing you need to know is the actual trajectory of your load from your rifle. To do this, you have to shoot it. One can calculate a great number of things, but you first need the actual performance data, not the book or webpage data. As an example, what if you are using a rifle with a different length barrel than the data in the book?? Your velocity will be different, and so will ALL your drop data, because of that. And, that's just one point.
Another point is how accurate you are judging the distance.
How certain are you that the buck is 276yds and not 237?
Third, you need to know whether a minor (vs. a gross) misestimation of the range will make a significant difference to the point of impact and the target area of the game. With your flat shooting 6.5mm a miss estimation of a few dozen yards won't make a large difference, the same amount of error shooting a different round (one with more drop) can make a huge difference, and it can be the difference between a clean kill, a wound, or a complete miss.
The answer is the same as the answer to the old joke about "how do I get to Carnagie Hall?"
PRACTICE!!
Most people use one of two basic methods. One method is to sight in precisely at a known distance (say 100yds), LEARN the trajectory, then using the adjustments in your scope, crank in the clicks for the range you are shooting at, and aim dead on. Then, REMEMBER to crank the scope BACK to where it was before the shot. Otherwise, you're going to have issues...
The other method is the same, but instead of adjusting the scope back and forth all the time, you set it for one distance, and then "hold over" (or under, dependent on the exact situation), and shoot.
Modern gadgets are wonderful, and allow for very precise adjustments, but the input has to be accurate or the outcome won't be.
One of the big drawbacks to changing the adjustments on your scope is the time required. For example let's say that the deer is at a distance where your bullet drop is 4" low from your sighted in point of impact. And, lets assume he's just standing there, waiting for you...
You can crank in 16 clicks up (to get 4" with a 1/4MOA adjustment scope) and aim dead on.
OR you can estimate and aim 4" higher on the deer, without adjusting the scope at all.
The second method requires experience, which you get through shooting practice. And practice is also the way to learn the OTHER important thing affecting your shots, WIND.
Bullets "drift" (are actually pushed) by wind. How much depends on MANY factors, bullet shape, speed, distance, wind speed and direction, (and wind can come from more than one direction and speed over the distance of the bullet's flight), etc.
There are charts that give approximate values, they can show you how bullet A at xxxxfps drifts X amount in a 10mph cross wind, Y amount in a 20mph crosswind, etc. BUT, they are guidelines, and no chart can give you the exact conditions you will encounter in the field.
DROP is a constant, wind is NOT. Real shame if you properly calculate the drop, crank it into your scope, and shoot that 276yd deer in the chest, only to have the bullet strike at the right height, but in the deer's guts not the chest cavity, because of wind drift.
Wind drift is kind of like leading a bird. Exactly how much lead is the right amount is something you have to learn to judge, and only practice will let you do that. There is a similarity with wingshooting, you need to learn how to correctly judge where the target and the shot will come together. The similarity is that you have to adjust your point of aim to hit where you want to hit.
At shotgun ranges, wind drift is seldom a vital factor. As range increases, so does the importance of being able to judge wind speed and direction between you and the target or you won't hit where you need to hit.
PRACTICE is the only way I know to learn these things. Go shoot on windy days, see how much left, right (and even up and down) different amounts of wind, and wind direction change where your shot hits on the target.
No book can tell you exactly. It can only give you guidelines, and you use those as a starting point adjusting for the widely variable real world conditions.
Shoot in as close to the conditions you will be hunting in, as possible. Shoot from field positions. If you're like most of us, you will find shooting from standing, sitting, kneeling and prone is quite different than shooting off a bench.
Good Luck!