Ammo & firearms
How loads, ammo, and firearms relate — matched by cartridge — why one ammo carries many loads, and why a velocity belongs to the load, not the ammo.
Three things you own, matched by cartridge:
- A load is a recipe (powder, charge, bullet, brass) with its own velocity — predicted from the recipe, or measured from its shots.
- Ammo is the shared exterior-ballistics identity its loads work under: cartridge, bullet, BCs (or a custom drag curve), the firearm, and an optional goal (target) velocity.
- A firearm is the barrel: cartridge, length, twist and direction, scope, and zero.
Ammo and firearm pair only when their cartridges match — always enforced, so you can’t dial a 6.5 load through a .308.
One ammo, many loads
One ammo groups many loads. Save your first load and its ammo is born with it; from there you develop more loads under the same ammo — several powders or charges, all aimed at one goal.
Each load keeps its own powder and charge, its own chronograph strings, and its own velocity — nothing is averaged across loads. Each is predicted and refereed on its own, so comparing them is an honest side-by-side, never a leaderboard. Factory-ammo shooters create ammo directly (no recipe) and log strings against it; handloaders log against each load — same immutable shots, same statistics either way.
Compare loads
The compare-loads view lines up each load’s predicted velocity against its measured velocity, both against the ammo’s target. It is the model’s self-test: where predicted and measured agree, the model earned its trust; where they diverge, the measurement wins. Nothing is blended — each load stands on its own numbers.
A velocity belongs to the load
A velocity is optional and belongs to the load, not the ammo: blank means “not established yet”, and it stays unknown — never a fabricated zero — until you measure or derive it.
The order of trust is fixed: your measured mean, then a value you stored or trued, then the model’s prediction with its interval and grade. The ammo’s goal velocity is only ever a target the loads aim at — never mixed in as though it were established.
A velocity is meaningless without its firearm, so the ammo carries the firearm its loads are shot in. The optional temperature coefficient (fps per degree) models powder-temperature sensitivity, referenced to 59 °F / 15 °C.
What the firearm supplies
A firearm supplies the twist (spin drift and stability), the scope (the dial-in-clicks column), and the zero. If your ammo has no cartridge yet, set it in one tap — then only firearms chambered for it are offered, or create one on the spot.