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Learn external ballistics from the ground up: safety, ballistic coefficient, sectional density, drag models, hunting energy, marksmanship, and long-range effects — each explained in plain language with the formulas that matter.
The four universal rules: treat every firearm as loaded; never point it at anything you aren't willing to destroy; keep your finger off the trigger until your sights are on target; and be sure of your target and what lies beyond it.
BC expresses drag performance relative to a reference model. For otherwise comparable loads using the same model, a higher BC generally means better velocity retention and less wind drift; drop also depends on muzzle velocity, zero, and conditions. It relates to sectional density and form factor as BC = SD ÷ form factor. Read the full guide.
Sectional density is bullet weight relative to diameter squared: SD = weight (gr) ÷ (7000 × diameter²). A 150-grain .308" bullet has an SD of about 0.226. It is one input associated with penetration potential; construction, impact velocity, stability, shot angle, and the target also matter.
Drag models are standard projectile shapes used to reference BC. G1 commonly describes traditional flat-base forms; G7 more closely matches many modern boat-tail designs. The values are not interchangeable through a fixed multiplier—use the published BC for the matching model.
About 1,000 ft-lb for deer-class game and about 1,500 ft-lb for elk-class game are commonly cited retained-energy references, not standards or minimums. A field limit also depends on current law, exact-load manufacturer guidance, demonstrated accuracy, shot presentation, and conditions.
Repeatable shot placement is supported by a stable position, natural point of aim, sight alignment, controlled breathing, and a clean trigger press with follow-through.
As time of flight grows, air density, spin drift, Earth's rotation, and the transonic transition can affect point of impact. Their significance depends on the load, conditions, direction, and precision required—not one universal distance.
Glossary · In-depth guides · Ballistic calculator · Methodology