How to use the tool

1 — Enter bullet data

• Bullet Weight (gr): e.g., 168 or 200.
• Bullet Diameter (in): e.g., 0.264 or 0.452.
• Ballistic Coefficient: 0.290 (varmint) or 0.615 (long-range).
• Drag Model: pick G1 (flatbase) or G7 (boat-tail).

2 — Add firearm parameters

• Muzzle Velocity (ft/s): 2550 or 3100.
• Zero Range (yd): 50 or 225.
• Sight Height (in): 1.2 or 2.0.
• Shooting Angle (°): −10 (downhill) or 12 (uphill).

3 — Record environment (optional)

• Temperature (°F): 20 or 95.
• Pressure (inHg): 28.90 or 30.25.
• Humidity (%): 15 or 90.
• Wind Speed (mph): 3 or 18.
• Wind Angle (°): 0 (headwind) or 135 (oblique).

4 — Formulas used by the JavaScript tool

The demo script simplifies exterior ballistics:

• Drop: $$\text{Drop}(d)= -0.0001\,d^{2}$$
• Velocity: $$v(d)=v_{0}-d$$ where (v_{0}) = muzzle velocity.
• Energy: $$E(d)=rac{0.5\,w\,v(d)^{2}}{450240}$$ with weight (w) in grains.
• Wind Drift: $$W(d)=0.0002\,d^{2}\,v_{\text{wind}}$$

5 — Worked example

Inputs: 200 gr, 0.308 in, BC 0.530 (G7), 2700 ft/s, zero 100 yd, wind 12 mph @90°.

• At 300 yd: Drop = −9.0 in.
• Velocity = 2400 ft/s.
• Energy = 2560 ft-lb.
• Wind Drift = 2.2 in.

Quick-Facts

• Standard G1 velocity bands assume a form factor of 1.0 [Berger Bullets FAQ].
• Air density falls ≈ 3% per 1 000 ft elevation gain (FAA Pilot’s Handbook, 2021).
• Gyroscopic stability factor > 1.4 recommended for accuracy (Miller, 2009).
• SAAMI maximum pressure for .308 Win is 62 000 psi [SAAMI Z299.4-2023].

FAQ

What is ballistic coefficient?

Ballistic coefficient (BC) expresses a bullet’s ability to overcome drag; higher BC retains velocity better (Litz, 2014).

How does wind angle change drift?

Drift equals full value at 90°; multiply by sine of the wind angle for other bearings (Applied Ballistics, 2022).

Why pick G7 over G1?

Boat-tail bullets match the G7 reference shape, giving ±2 % drop error to 1 000 yd, versus ±5 % with G1 (Bryan Litz, 2016).

How do I measure sight height?

Measure from bore centerline to optic center; typical AR-15 height is 2.6 in (Magpul Armorers Manual, 2020).

What environmental factor matters most?

Pressure changes bullet drop nearly 1 MOA per 1 000 ft altitude shift (USMC Scout-Sniper Course, 2019).

Can the simplified formulas replace full solvers?

No; they ignore drag curve shifts at Mach transitions, reducing accuracy beyond 600 yd (Lapua Ballistics Guide, 2023).

How often should I re-zero?

Re-zero whenever ammunition, altitude, or seasonal temperature changes by > 20 °F (Hornady Handbook 11th Ed., 2022).

What unit conversion should I remember?

1 mil equals 3.6 in at 100 yd, useful for quick holdovers (NRA Instructor Guide, 2021).