The letters after a cartridge name are not decoration. Each tells you where the cartridge came from and how it behaves.

Seven-millimeter ammunition is full of initials. Here is what they stand for and what each one tells you.

Letters that name a purpose

SPC is short for Special Purpose Cartridge. The 6.8 SPC was developed with U.S. special operations in mind for the AR-15, and its polymer-tip loads are at 6.8 spc polymer tip ammo.

PRC stands for Precision Rifle Cartridge, a Hornady label for cartridges designed for long-range work. The 7mm PRC's 175-grain loads are at 7mm prc 175 grain ammo.

Letters that name a maker's family

RUM is Remington Ultra Magnum, the largest case of the group, and the 7mm RUM's loads are at 7mm rum ammo. SAUM is Remington's Short Action Ultra Mag, the same idea in a short case, and Nosler's loads for it are at nosler 7mm saum ammo.

WSM stands for Winchester Short Magnum, and STW for Shooting Times Westerner, a wildcat named for the magazine that popularized it. Weatherby needs no initials, because its magnums carry the founder's name. The 7mm Weatherby Magnum is at 7mm weatherby magnum ammo for sale.

Letters and numbers that describe the case

The R in names like 7x57R stands for rimmed. Numbers such as 7x64 give the bullet diameter and the case length in millimeters, and the name after them, here Brenneke, credits the designer. The 7x64 Brenneke's 140-grain loads are at 7x64 brenneke 140 grain ammo.

The 08 in 7mm-08 points to the .308 Winchester case it grew from, and its loads are at 7mm-08 ammo. The 7mm Remington Magnum drops the numbers but keeps the maker's name, and polymer-tip loads for it are at 7mm rem mag polymer tip ammo.

Words that are just words

Not every label is technical. Backcountry is a name that points at mountain hunting, and anyone who wants to buy 7mm backcountry ammo should still check the chambering. Western is simply the name of Winchester and Browning's 2021 short magnum, and anyone who wants to buy 6.8 western ammo is shopping for that cartridge.

Initials are shorthand, not a guarantee of fit. Match the full cartridge name on your barrel to the box, and confirm current stock and state shipping restrictions before ordering.