Bullet names mix two independent things: what the bullet is made of and shaped like at the front (which mostly governs what happens at the target), and what its rear and profile look like (which governs how it flies). Only the second is external ballistics, but the vocabulary is shared, so it is worth laying out both.
Core and jacket
Full metal jacket (FMJ). A lead core fully enclosed in a harder jacket, usually gilding metal, with the jacket closed at the nose and open at the base. Cheap, feeds reliably, and does not deform. Military ball ammunition — M193, M855, the 7.62×51 M80 — is FMJ.
Soft point (SP). The jacket stops short of the tip, exposing lead. Designed to expand on impact. The standard hunting construction for a century.
Hollow point (HP). A cavity in the nose. In a hunting bullet the cavity is there to initiate expansion. In a match bullet it is there for a completely different reason, which causes endless confusion — see below.
Polymer-tipped. A plastic tip filling what would be a hollow point. It gives the aerodynamic advantage of a sharp point without the fragility of a thin lead or jacket tip, and drives expansion on impact. Hornady’s V-MAX/ELD, Nosler’s Ballistic Tip, Sierra’s Tipped MatchKing all work this way. ELD-class tips use a heat-resistant polymer specifically because ordinary plastic tips can deform from air friction on long flights, which changes the effective BC.
Monolithic / lead-free. Turned from solid copper or a copper alloy, with no lead core. Barnes TSX and similar. Because copper is less dense than lead, a monolithic bullet of a given weight is longer than a lead-core one — which matters for twist rate and case capacity. Increasingly relevant in Europe as lead restrictions come in.
Bonded and partitioned. Constructions that hold the core to the jacket (bonded) or split the bullet into a front section that expands and a rear that does not (Nosler Partition). Terminal engineering; aerodynamically these behave like ordinary soft points.
Base and profile — the part that matters in flight
Flat base. The rear is a flat disc. Simple, and often excellent at short and medium range. It produces a larger base wake and therefore more base drag than a tapered rear.
Boat tail. The rear tapers to a smaller diameter, typically over 7–13°. This reduces base drag substantially at supersonic speed, which is where most of the drag of a well-shaped bullet comes from. A boat tail is the single biggest aerodynamic difference between a 1900s-profile bullet and a modern one, and it is exactly what the G7 reference projectile has and the G1 reference does not. That is why boat-tail bullets are better described by G7 BCs.
Ogive. The curve of the nose. Longer, sharper ogives (secant profiles, “very low drag” designs) cut wave drag. They are also fussier about how far they sit from the rifling. A “tangent” ogive is more forgiving and slightly draggier.
Meplat. The tiny flat at the very tip. Small variations in it produce measurable BC variation between bullets from the same box — which is why some long-range competitors trim and uniform their meplats.
Open-tip match — not a hollow point in the usual sense
An OTM or HPBT match bullet, such as the Sierra MatchKing or Hornady BTHP, has a small opening at the nose. It is not there to expand. It is a by-product of the manufacturing method: the jacket is drawn from the nose backwards and the core seated from the rear, which puts the jacket seam at the base rather than the tip. A base-seamed jacket is more concentric, and concentricity is what makes a match bullet shoot well.
The practical points that follow:
- Match bullets are optimised for precision, not terminal effect, and their expansion behaviour is inconsistent by design.
- The tiny cavity has minimal aerodynamic cost, but the variation in it between individual bullets does affect BC consistency.
What this means for the calculator
Only three things you enter come from construction: mass, diameter and BC (with its drag model). Everything else — expansion, fragmentation, penetration — happens after the flight this tool models ends.
The rule of thumb worth carrying: boat tail plus long ogive → use the G7 BC; flat base or blunt profile → G1 is the honest fit. And whatever the box says, a bullet’s real BC is best confirmed by shooting it.