Dillon Learning Center

The Reloading
Glossary

A

Anvil

The internal portion of a Boxer primer that allows the firing pin strike to crush the priming compound and ignite the primer. On Berdan primed cases, the anvil is integral to the primer pocket, so the flash holes are off-center.

B

Belted

An integral ring of brass just above the extractor groove on a (usually) bottleneck case. Originally necessary on cartridge cases that didn't have enough shoulder angle to maintain chamber headspace, such as 300 and 375 H&H cartridges. As it adds yet another working tolerance to the case design, most modern magnum cases have eliminated the need for this belt with better case design.

Berdan

A primer design made up of just the primer cup and the primer compound. The anvil is integral to the case. Berdan primed cases cannot be deprimed during the sizing step, as the flash hole(s) are offset from the center of the primer pocket. Berdan primers have different dimensions than Boxer primers and are not interchangeable.

Boxer

The predominant primer used in America. Boxer primers are made up of the primer cup, the priming compound, and the anvil. Boxer primed cases have a single central flash hole and can generally be pushed out during the case sizing process.

Bullet

The projectile - the part pushed out the front of the barrel when the cartridge is fired.

A cartridge is not a "bullet".

C

Caliber

The diameter of the bullet. Can be expressed in thousandths of an inch (.308") or in metric (6.5mm).

Cannelure

A dotted line embossed into the bearing surface of a jacketed bullet. A location to crimp the case into, as well as a suggested seating depth - not a rule, more of a guideline.

Cartridge

A complete, ready-to-fire single round of ammunition. The cartridge for a specific chambering has a name, such as 6.5 Creedmoor or 45ACP.

Case

The metal or polymer container that fits the chamber of a firearm and secures the primer, powder, and bullet in place. Reloadable rifle and handgun cases are typically made of brass. Shotshell cases are made of polymer with a metal flanged base.

Centerfire

A case with a separate primer inserted into a recess in the head of the case.

Chamfer

A process performed on bottleneck cases to bevel the inside and outside of the case mouth. This prevents damage to the case or bullet when the bullet is seated.

Crimp

To either curl the case mouth into a crimp groove or cannelure in the bullet (roll crimp), or to squeeze the case mouth firmly against the side of the bullet (taper crimp). This prevents the bullet from being pushed deeper into the case when chambered, or from sliding forward out of the case mouth under recoil.

When loading match rifle cartridges, it is recommended to avoid crimping altogether.

D

Depriming / Decapping

The action of pushing the fired primer out of the case. Usually performed in the size die, but in some circumstances done as a separate step.

Die / Die Set

A precision tool, or set of tools, that processes a fired case back into a loaded cartridge through multiple steps.

E

Extractor Groove

The circumferencing groove near the bottom of the case that the extractor grabs to withdraw the case from the firearm chamber.

F

Flare

Straight-wall and tapered cases need the case mouth flared outward about .010-.020" so that when bullets are seated, the case mouth doesn't shave material off the bullet and the case isn't collapsed during seating.

Flash Hole

The small hole (usually .075" in diameter) in the primer pocket that allows primer ignition to ignite the powder charge. The depriming pin passes through this hole to push the fired primer out of the case.

G

Grain

A unit of weight measurement for powder charges. There are 7,000 grains per pound of powder, and the minimum weight unit is 1/10th of a grain.

A grain is NOT a granule of powder.

H

Headspace

The distance from the breechface of a firearm to the point on the case that stops forward movement in the chamber. On rimmed cases this is the thickness of the rim. On straightwall and tapered cases this is the dimension to the case mouth. On bottleneck cartridges this is to a datum line in the middle of the shoulder. A headspace gauge is necessary to measure this on bottleneck cases.

L

Lube Dent

A temporary deformity in the shoulder of a bottleneck case, caused by a buildup of case lubricant in the size die. These are cosmetic only and get smoothed out when the cartridge is fired.

N

Neck

The upper part of the case that holds the bullet securely. During resizing, the case neck is sized to smaller than the bullet diameter so the bullet is a press fit.

Neck Sizing

On bottleneck cases, if the fired cases are only being used in the same chamber and in a bolt action or single shot rifle, you can resize just the case neck - leaving the rest of the case at fired dimension. This can result in a minor improvement in accuracy.

O

Ogive

The shape of the curved portion of the bullet. Minor manufacturing variations in the ogive will result in variations in overall cartridge length.

P

Powder

The propelling charge that forces the bullet down the barrel. Smokeless powders are considered a solid propellant under fire code - they burn quickly but are not an explosive. Black powder, most frequently used in muzzle loading and early cartridge firearms, is an actual explosive.

Priming

The action of seating a new primer into a case.

R

Rebated

When the rim of the bottom of the case is smaller than the base of the case, measured just above the top of the extractor groove.

Resize

The action of forcing the fired case into a machined die, which squeezes the case back to a dimension that will fit the chamber and securely hold a bullet in the case mouth. Typically, the fired primer is pushed out of the primer pocket during this process.

Rimfire

The case has a protruding rim that contains the priming compound. The firing pin strikes the edge of this rim to set off the priming charge. Rimfire cases are difficult to reload - the soft rim deforms where the firing pin strikes it, and due to the thin rim material required, rimfire cartridges are lower pressure than centerfire cartridges.

22 Long Rifle, 22 Magnum, and .17 HMR are the most common rimfire cartridges. These are generally considered non-reloadable.

S

SAAMI

The Sporting Arms and Ammunition Manufacturers Institute. The organization that standardizes and approves ammunition specifications.

Seating

The action of pushing a bullet into the case mouth. The seating die allows you to adjust how far the bullet is pushed in and holds the case and bullet in alignment while the bullet is seated.

Squib

A cartridge assembled without any powder. When discharged, the primer usually has enough energy to push the bullet at least partway into the barrel. The primer typically also backs partway out of the case.

Swaging

The action of removing the crimp surrounding a primer pocket. Ammunition loaded for military use - or on military equipment - crimps the primer into the pocket after seating to prevent it from backing out on a squib. The fired primer deforms enough to push past this crimp, but the crimp must be removed before a new primer can be seated.