BallistaBallistics guides
What the bullet does after it leaves the barrel.
Wind, drop, air and the corrections in between, explained the way you'd explain them at the bench. Every number is solved with the Ballista engine, and every rule of thumb is checked against a full solution.
FoundationsTrajectory, angles, BC and the inputs you control
- 01How a trajectory worksWhy a bullet crosses your line of sight twice but never rises, where the two crossings fall for a 100 and a 200 yard zero, and why changing the zero shifts every come-up by the same angle.
- 02MIL vs MOAExact MIL and MOA conversions, why 1 MOA is not 1 inch at 100 yards, how to range with the mil-relation formula, and what each shortcut costs at 600 and 1,000 yards with a 6.5 Creedmoor.
- 03G1 vs G7 BCFor a long boat-tail bullet the G1 BC that matches the real path holds steady above Mach 1.7 and then slides fast. Where a single G1 number starts to miss for a 6.5 Creedmoor and a .308, and by how much.
- 04Muzzle velocity vs BCA 25 fps velocity error and a 5% BC error, solved side by side to 1,000 yards: where each one dominates, what your chronograph's SD does to vertical, and why truing at 600 yards can still miss at 1,000.
- 05Sight height and zeroA 1.5 vs 2.5 inch scope height and a 100 vs 200 yard zero, solved from 5 to 1,000 yards: big holds up close, a constant offset far away, and the sight height mistake that costs a click at 1,000.
- 06Building a DOPE cardWhich columns a DOPE card needs, what step size costs if you read the nearest row, how far to print, and how far a card made at sea level goes wrong at 3,000, 6,000 and 9,000 feet of density altitude.
AirDensity, pressure, temperature, humidity
- 07Density altitudeWhat density altitude measures, how it is computed from pressure, temperature and humidity, what 5,000 and 10,000 ft do to your come-ups, and why two days with the same DA can still need different holds at 1,000 yards.
- 08Station vs barometric pressureThe weather report's pressure is corrected to sea level; your bullet flies through the real one. At a 5,000 ft range, mixing them up sends a .308 over a 12-inch plate from 600 yards out. The worked example, the reverse mistake, and how to tell the two apart.
- 09Temperature: air and powderCold air and cold powder both make you dial more, for different reasons. We split the two on 20°F and 90°F days for a 6.5 Creedmoor and a .308, and find the powder sensitivity at which the powder starts to outweigh the air.
- 10HumidityHumid air is lighter than dry air, so a muggy day needs slightly less elevation. We solved 0% against 100% humidity from 20°F to 100°F: how many feet of density altitude it is worth, and what it moves at 1,000 yards.
WindDrift, calls, angles and the vertical part
- 11Wind drift and lag timeWhy a 6.5 Creedmoor drifts 39% less than a .308 while spending only 16% less time in the air, how to learn one wind number per range, and what a 2 mph wrong call costs at 600 and 1,000 yards.
- 12Calling wind with a bracketHow wide a ±1.5 and ±3 mph wind bracket is in MIL from 300 to 1,000 yards, how to turn the first impact into a measured wind speed, and why you should carry miles per hour to the next target, not mils.
- 13Wind angles and clock valuesA 2 o'clock wind is 87% of full value, not half. We test the full, half and no value convention against the exact solution at 600 and 1,000 yards and show why direction errors hurt most in a near-headwind.
- 14Headwind, tailwind and jumpA 10 mph headwind barely moves a 6.5 Creedmoor at 1,000 yards. A 10 mph crosswind moves it vertically more. How much head and tail winds change elevation, how crosswind jump works, and which way it goes.
Long-range effectsSpin drift, Coriolis, transonic flight, slope and cant
- 15Spin driftSpin drift for a 6.5 Creedmoor and a .308 from 100 to 1,200 yards, the range where it passes one click, how twist and stability change it, and why the .308 drifts more than the faster-twist 6.5.
- 16CoriolisHow far the Earth's rotation moves a 6.5 Creedmoor and a .308 at 1,000 yards by latitude and shot direction, why shooting east lands high, and the distance where it finally reaches one click.
- 17Transonic flightWhere a 6.5 Creedmoor and a .308 drop below Mach 1.2 and Mach 1 from sea level to 10,000 ft, what the G7 drag curve does near the speed of sound, and what really extends your supersonic range.
- 18Uphill and downhillWhy you hold less on any slope, why uphill and downhill aren't quite the same, and how far the rifleman's rule and the cosine rule drift from a full solution at 15, 30 and 45 degrees out to 900 yards.
- 19CantTwo degrees of tilt puts a 6.5 Creedmoor a foot right at 1,000 yards and barely moves it down. Why cant misses sideways, and why the sine rule of thumb comes up short.
Field practiceTruing, MPBR, hit probability, scopes and holds
- 20Truing your solutionStep-by-step truing at one to three distances: where velocity truing works and where drag truing has to take over, how many shots a group needs, and how a two-distance true fixes a .308 to 1,000 yards.
- 21Maximum point-blank rangeThe best zero for 4, 6 and 8 inch vital zones with a 6.5 Creedmoor, a .308 and a .270 deer load, how far each holds dead on, and why sighting in 3 inches high at 100 yards is an 8-inch rule.
- 22Hit probabilityA Monte Carlo error budget for a 12-inch plate at 600 and 1,000 yards: wind call, range, velocity spread and rifle precision, solved with the engine. The wind call accounts for more of the miss than the other three combined.
- 23Scope trackingHow to run a tall target test, turn it into a tracking factor and correct your come-ups, what a turret that moves 3% too far does at 1,000 yards, and why truing velocity can hide it.
- 24Holding with a reticleHoldover tables for a 6.5 Creedmoor and a .308 in MIL and MOA, what a second focal plane reticle does to every hold when you turn the power down, and when holding beats dialing.
- 25Ranging with a reticleThe mil-relation formula in MIL and MOA, how far off a 0.1 mil misread or a wrong target size puts your range at 300 to 800 yards, and how many inches that error moves the impact on an 18-inch plate.
- 26Leading moving targetsLeads for a 3 mph walking animal and a 5 mph steel mover from 200 to 600 yards, in inches, MIL and MOA, and why the lead in angle grows far slower than time of flight.
Gear by the numbersCartridges compared on the same day
- 276.5 CM vs .308 vs .300 WMThree match loads solved in the same air from 300 to 1,200 yards: come-ups, 10 mph wind drift, velocity and energy, and why the .300 Win Mag drops least but drifts more than the 6.5 Creedmoor.
- 28.22 LR at distanceDrop and 10 mph wind drift to 300 yards for a subsonic match load on RA4 drag and three CCI loads, why a .22 drifts like a .308 at several times the distance, and where high-velocity loads go transonic.
Questions shooters askForum questions answered with full solutions
- 29Re-zero at altitudeA rifle zeroed at sea level and carried to a 9,000 ft density altitude: how far the zero itself moves at 100, 200 and 300 yards, how far the 400 to 600 yard holds move, and when a re-zero is the right call.
- 30Max ethical rangeBullet velocity, wind-call error and your own precision each set a maximum range on an 8-inch vital zone. We solve all three for a 6.5 Creedmoor and a .308 hunting load at sea level and 8,000 ft, and find which comes first.
- 31Drops don't matchSeven common input mistakes solved against a 6.5 Creedmoor's true trajectory to 1,000 yards. They fall into three shapes, and your miss at two distances tells you which one you have before you true anything.
- 32Box velocity vs yoursThe box says 2,710 fps from a 24-inch test barrel. Your 20-inch rifle is slower. How far that moves your impacts from 300 to 1,000 yards, where it moves the transonic zone, and why truing at 300 yards can't find it.
- 33ES and SD on targetInches of vertical per fps of standard deviation for a 6.5 Creedmoor and a .308 at 300, 600 and 1,000 yards, what that does to a half-MOA rifle's groups, and how little a 5-shot string tells you about your real SD.
- 34Custom turrets at another altitudeAn engraved yardage turret is a DOPE card for one air. We dialed a turret cut at 1,000 ft at 5,000 and 9,000 ft and on 20°F and 90°F days, found where it misses an 8 inch vital zone, and what a mid-altitude engraving buys.
- 35Elevation budget and the 20 MOA baseCome-ups at 1,000 and 1,200 yards for a 6.5 Creedmoor and a .308 in cold, standard and thin air, set against 60, 80 and 100 MOA of scope travel on a flat base and a 20 MOA base.
- 36Updrafts and downdraftsAir moving up or down pushes the bullet exactly as far as the same crosswind pushes it sideways. Numbers from 300 to 800 yards, an updraft over only part of a canyon, and the updraft behind a 0.7 mil high miss at 370 yards.
- 37Zeroing at 25, 36 or 50 yardsA dead-on 25 yard zero is not a 100 yard zero. How far low to hit at 25 for your sight height, where 25, 36 and 50 yard zeros cross again, and why any error at 25 is four times larger at 100.
- 38Muzzle wind or target wind?We put a 10 mph crosswind in one third of a 600, 800 or 1,000 yard path at a time. The third nearest the rifle causes about half the drift, the third nearest the target about a sixth. Why, and how to weight a call.