Understanding ballistics
Ballistics is what happens to a bullet from the moment the primer fires to the moment it stops. You don't need the physics. You need a few ideas that explain why bullets drop, why wind matters, and why the numbers on the box are worth reading.
Every shot happens in three stages
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1Inside the barrel
The primer lights the powder, gas pressure builds, and the rifling spins the bullet. Barrel length and the load decide how fast it leaves.
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2In flight
Gravity pulls it down, air slows it, and wind pushes it sideways. This stage decides where the bullet lands.
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3On target
How the bullet expands, penetrates, and holds together. This stage decides what the bullet does when it gets there.
Read the numbers on the box
Most ballistic information you need is already printed on the box or the manufacturer's product page. Here's what each number tells you.
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1Caliber
The cartridge name. It has to match what's stamped on your gun.
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2Grain (gr)
Bullet weight. Heavier bullets usually leave slower but hold speed and resist wind better.
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3Bullet type
How it's built, which controls what happens on target. FMJ, hollow point, soft point, and so on.
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4Velocity (fps)
Speed leaving the barrel, in feet per second. It's measured in a test barrel, so your gun may run faster or slower.
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5Energy (ft-lb)
The bullet's punch, calculated from its weight and speed. Speed counts more than weight.
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6Ballistic coefficient (BC)
How slippery the bullet is in the air. Higher BC holds speed longer, drops less, and drifts less in the wind.
Why bullets drop
Gravity starts pulling the instant a bullet leaves the barrel. Your scope is tilted down slightly so the bullet arcs up through your line of sight and back down again.
Diagram not to scale.
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1First crossing
The bullet starts below your scope and climbs up through the sight line a short way out.
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2The peak
It rises a little above where you're aiming before gravity takes over.
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3Your zero
It crosses back down at the distance you zeroed. That's where point of aim equals point of impact.
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4The drop
Past your zero, drop grows faster and faster as the bullet slows. That's why long shots need a holdover or a scope adjustment.
Common zero distances
Handguns: 15 to 25 yards. AR-15s: a 50-yard zero puts most 5.56 loads close to on again around 200 yards. Hunting and precision rifles: 100 yards is the standard starting point, and some hunters prefer 200 for a flatter point-blank range.
Reading the wind
Wind is the hardest part of ballistics because you can't see it and it changes between you and the target. Two ideas cover most of it.
Direction matters as much as speed
Picture a clock with your target at 12. Wind from the side, anywhere from 2 to 4 or 8 to 10 o'clock, has full or nearly full effect. Wind at a steep angle, from 1, 5, 7, or 11 o'clock, has about half. Wind straight from behind or ahead barely moves the bullet sideways.
Distance multiplies everything
A breeze that moves a rifle bullet an inch at 100 yards can move it a foot or more at 500, because the bullet is slower and in the air longer. Higher-BC bullets drift noticeably less.
Watch flags, grass, leaves, and dust between you and the target. Shooting at longer distances? Mirage through a scope shows the wind at the target.
Target at 12 o'clock, you at the center.
Quick facts that surprise people
A few more effects worth knowing, especially if you hunt in the mountains or shoot across seasons.
Uphill or downhill, aim lower
Steep shots in either direction hit higher than you'd expect. Use the horizontal distance to the target, not the straight-line distance, to pick your holdover.
Thin air shoots flatter
At higher elevations the air is thinner, so bullets slow down less and drop less than they do at sea level.
Cold air shoots lower
Cold air is denser, and some powders burn slower when cold. Both can lower your point of impact in winter.
Your barrel changes the speed
Short barrels give up velocity, so a load will usually run slower from a carbine or compact than the number on the box.
What happens on target
Terminal ballistics is the part that matters most for hunting and defense. A bullet has to arrive with enough speed to work as designed: hollow points and hunting bullets need a minimum velocity to expand, and that velocity drops the farther out you go.
That's why bullet construction matters as much as caliber. Our ammo selection guide breaks down which bullet types fit which jobs.
Read the selection guidePut it to work
- Zero your rifle with the exact load you'll use.
- Find your real velocity with a chronograph, since your barrel won't match the box.
- Run a ballistic calculator with your bullet's BC and your velocity to get drop and wind numbers.
- Confirm at distance. Shoot at real ranges and adjust the calculator to match.
- Write it down. A data card taped to your stock beats guessing in the field.
Common questions
Do heavier bullets drop more?
Usually they leave the barrel slower, so they drop more at moderate ranges. But heavy bullets often have higher BCs and hold their speed better, so at long range they can catch up and sometimes drift less in the wind.
Why does my ammo hit differently than the last brand?
Different bullet weights, shapes, and velocities fly differently, even in the same caliber. Re-check your zero any time you change loads.
What's the difference between G1 and G7 BC?
They're two different reference shapes for measuring drag. G7 better matches long, boat-tail bullets used for long range, which is why many match bullets list it. Use whichever your ballistic calculator asks for.
Is more energy always better?
No. Energy is a useful comparison number, but shot placement and bullet construction matter far more for results on game. A well-placed shot with the right bullet beats a bigger number every time.
What's subsonic ammo?
Ammo that travels slower than the speed of sound, roughly 1,100 fps. It's quieter, especially with a suppressor, but it drops faster and needs a bullet designed to expand at low speed.
Ready to stretch your range?
Match-grade and long range loads with published BCs and consistent velocity.