When it comes right down to it, there are quite a few factors that play into long range hunting.
Success in the field is most often a product of effective training on the range — the execution of several basic principles that include using the right calibers, adjusting for wind and using the correct shooting mechanics.
It seems simple, but as any honest shooter will tell you, we've all screwed it up more than once. The best way to address problems you're facing with long-range hunting is to examine the most common reasons for long range hunting misses and make sure you're not committing one of these grievous errors. If you've addressed these issues, your problems will be greatly diminished.
You're Using the Wrong Bullet
Bullets are not all created equal. Just as some bullets are designed to withstand high velocities and expand reliably in game animals, others are also engineered to battle the forces of physics — only a few are designed to do both. Bullets with high ballistic coefficients are better suited for long range work because they are more aerodynamic.
Competitive shooters very rarely use light-for-caliber bullets, which in theory would shoot flatter at long range. In reality, though, long, heavy-for-caliber bullets do a better job resisting crosswinds and retain more velocity and energy downrange. Spitzer-type bullets with boat tail design (to reduce drag) are a good choice for long range hunting.
You Misjudged the Distance
If you aren't very good at judging distance, don't despair — you're part of the majority. Military tests have shown humans just aren't very good at accurately judging long distances, and unfamiliar terrain only compounds the problem. If you're planning on taking shots at extended ranges, you need to keep a quality rangefinder in hand.
Some hunters are very good at using their scope to judge the body depth of the animal in regard to demarcations within the scope itself at a certain magnification —a graduated reticle helps — but this technique is still only an estimate at best. There are a number of excellent rangefinders available today at reasonable prices, so pick one up for long range shooting. Why guess when you can know for sure?
You Didn't Account For the Wind
I've known several hunters that could recite ballistic tables for their favorite load like it was their phone number, but when asked about the wind these same hunters stammered and scratched their heads in despair. Judging crosswinds?
That's no fun, because while a bullet's drop based on gravity over flat ground will remain virtually the same under most circumstances, wind drift is far more dynamic.
Wind gusts and changes direction, and it may be calm at your position with a steady breeze at the target, or vice-versa. Learning to cope with the wind takes practice, and out to about 200 yards normal wind drift isn't usually enough to throw the bullet completely out of the kill zone. However, at 400 yards that same steady breeze might mean a crippling shot instead of a clean kill.
Most ballistics charts show wind drift with a 10 mph wind blowing parallel to the shooter. Wind coming at an angle will cause the bullet to drift less than direct parallel force. The best tip here is to practice your shooting on windy days when other shooters stay on the couch.
You Rushed the Shot
Long range shooting is as much a mental challenge as a physical one. It requires the shooter to be relaxed and composed, but suddenly getting a shot at a once-in-a-lifetime buck isn't conducive to relaxation and composure. Long range shooting is precision shooting, and the very best shooters have the ability to keep control of their emotions.
Learning to compose yourself is a direct result of practicing fundamentals on the range again and again until it becomes habit. At that point, even though you are thrilled to see that big buck, you will fall back on your training on the range.
Practice controlling your breathing, focusing on your sight picture, good body position and steady, direct trigger pressure. If the animal is moving or angled badly, wait for your chance, keep yourself composed and ready to go when the opportunity presents itself.
You're Shooting a Gun With Too Much Recoil
Shooting game at long ranges requires precision, and precision requires the shooter to control their fear and deliver the shot without flinching. Most long range cartridges are fast and powerful, but just because a rifle is chambered for a magnum cartridge doesn't mean it's automatically going to be abusive.
I've shot plenty of magnums that weren't painful, usually because they fit me well, had a good stock, an effective recoil pad and enough heft to reduce the punch. The key is finding a gun you are comfortable with and learning how to shoot it well. If you're experiencing pain, it's time to call it a day, because once you've established a flinch it's a hard habit to break and it will plague your shooting.
You're Using Ammo That Isn't Producing Consistent Velocities
Consistency is one of the keys to accuracy, and if your ammo isn't producing consistent velocities then you're doomed from the start. It's well worth buying a chronograph as a diagnostic tool to determine whether or not your ammo is living up to its end of the bargain.
Calculating the standard deviation of the velocity of your ammo may initially seem like a lot of work, but if you are serious about shooting well at long range it is certainly worth your time and money to purchase a quality chronograph to check the velocity claims on your ammo box.
Another option is to contact a custom loading company like Superior Ammunition that will load cartridges to your specs (within reason), assuring you that you won't have velocities that are as scattered as the bullet holes in your target.
You've Never Actually Practiced at Long Range
Seems simple enough, right? You wouldn't try to ski a black diamond after a half-day fundamentals course on the bunny slopes, so why would you try a 400 yard shot when you've never shot your rifle farther than 100 yards at the range?
I know, I know, you've read ballistics charts and you know exactly what your bullet is going to do at 200, 300, 400 yards and beyond. It's right there in black and white, isn't it?
Actually, there are a variety of factors that can affect bullet performance at long range. First off, how consistent are your velocities? What length of barrel was used when the ballistics tests were being conducted, and does it match what you have on your rifle?
How about bullets with varying ballistic coefficients? How will wind affect your shot? What does a target look like through your scope at 400 yards?
Bottom line, developing confidence at the range will translate to success in the field. The better your grasp on these basic shooting principles and most common long range hunting mistakes, the better chance of success you'll have when a trophy is in your sights.