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.
Belted
An integral ring of brass just above the extractor groove on a (usually) bottleneck case. This was 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 that is 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, head, by whatever name, the part that is pushed out the front of the barrel when the cartridge is fired. NOTE: a cartridge is not a “bullet”.
Caliber
The diameter of the bullet; can be expressed in thousandths of an inch (.308”) or in metric (6.5mm).
Cannelure
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
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 to bottleneck cases to bevel the inside and outside of the case mouth. This prevents damage to the case or the bullet when the bullet is seated into the case.
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 either getting pushed deeper into the case when the round is chambered or prevents recoil from allowing the bullet to slide forward out of the case mouth. When loading match rifle cartridges, it is recommended to avoid crimping altogether.
Depriming / Decapping
The action of pushing the fired primer out of the case. This is usually performed in the size die, but in some circumstances depriming is done separately.
Die / Die Set
A precision tool, or set of tools, that process a fired case back into a loaded cartridge, requiring multiple steps.
Extractor Groove
The circumferencing groove near the bottom of the case that the extractor grabs to withdraw the case from the firearm chamber.
Flare
Straight-wall and tapered cases need the case mouth flared outward about .010-.020” , so that when bullets are seated into the case, the case mouth doesn’t shave any material off the bullet, and the case isn’t collapsed when the bullet is seated.
Flash Hole
The small hole (usually .075” in diameter) in the primer pocket that allows the primer ignition to ignite the powder charge. The depriming pin passes through this hole to push the fired primer out of the case.
Grain
A unit of weight measurement for powder charges. There are 7,000 grains per pound of powder, and a minimum weight unit is 1/10th of a grain. Be aware, a grain is NOT a granule of powder.
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. For bottleneck cases, a headspace gage is necessary to measure this with.
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.
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 are being used in a bolt action or single shot rifle, you can just resize the case neck to hold the bullet, leaving the rest of the case at the fired dimension. This can result in minor improvement in accuracy.
Ogive
The shape of the curved part of the bullet. Very minor manufacturing variations in the ogive of the bullet will result in variations in the overall cartridge length.
Powder
The propelling charge that forces the bullet down the barrel and to the target. Smokeless powders are considered a solid propellent 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.
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 pullet 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, as the soft case rim deforms where the firing pin strikes it. In order to reload rimfire cases, this deformation must be pushed out, the groove in the case rim that contained the priming compound must be cleaned, and new priming compound applied. This cannot be done mechanically. Additionally, due to the soft, thin rim material required, rimfire cartridges are lower pressure than centerfire cartridges. 22 Long Rifle, 22 Magnum and .17 HRM are the most common examples of rimfire cartridges. These are generally considered “non-reloadable”.
SAAMI
The Sporting Arms and Ammunition Manufacturers Institute. This is 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 with each other while the bullet is seated.
Squib
A cartridge assembled without any powder in it. When discharged, the primer usually has sufficient energy to push the bullet at least partway into the barrel. Additionally, the primer typically backs partway out of the case.
Swaging
The action of removing the crimp surrounding a primer. Ammunition loaded either for military use – or on military equipment – crimps the primer into the pocket after it is seated. This is done to prevent the primer from backing out of the case in the event of a squib. The fired primer will easily deform to be pushed out past this crimp. However, this crimp must be removed before a new primer can be seated into the case.
