Handgun Ammunition Info
DIAMETER / CALIBER
This measurement refers to the diameter of the bullet or projectile (and the corresponding internal diameter of the barrel). Diameter translates to caliber, and it's the most important spec, as it roughly relates to the name of the cartridge, too. Caliber is the term you're probably most familiar.
A cartridge's measurement is listed in either hundredths of inches or millimeters. Let's start with 9mm. This round, the most popular handgun cartridge in the world, utilizes a nine-millimeter (or .35-inch) diameter bullet.
Common Pistol Calibers (measured in millimeters)
9mm
10mm
Common Pistol Calibers (measured in hundredths millimeters)
.22
.380
.38
.40
.44
.45
Most cartridges are properly named based on diameter (i.e., like the 9mm, the .45ACP bullet is actually .45 inches in diameter). Others are only close. The .38 special round, the most-common revolver cartridge, utilizes a .357-inch bullet diameter, which is actually closer to .36 caliber.
GRAIN
When it comes to buying ammunition, the "grain" indicated on the box actually refers specifically to the weight or mass of the bullet. Grain is a unit of measure. There are 7,000 grains in a pound and 437.5 grains in an ounce.
A 230-grain, .45-caliber bullet weighs .525 ounces, a little more than half an ounce.
A 115-grain, 9mm bullet weighs .262 ounces, half the weight of the 230-grain bullet.
To make it more interesting, European ammunition is measured in grams. That same 115-grain, 9mm bullet weight would be listed as 7.45 grams.
Common Bullet weight in Grains (.380 Caliber)
95 gr
Common Bullet weight in Grains (9mm Caliber)
115 gr
124 gr
147 gr
Common Bullet Grains (.40 Caliber)
165 gr
180 gr
Common Bullet Grains (10mm Caliber)
180 gr
200 gr
Common Bullet Grains (.45ACP Caliber)
185 gr
200 gr
230 gr
The heaviest, most commonly found 9mm round (a 147-grain bullet) is still lighter than one of the lightest-weight .45ACP rounds (185 grains). Depending on preferences and what are trying to accomplish with pistol, choose a heavier or lighter bullet weight.
VELOCITY
Typically for a given cartridge, the heavier the bullet weight, the lower the velocity, and the lighter the bullet, the higher the velocity. Bullet grain varies based on caliber and manufacturer guidelines. But generally speaking, smaller caliber rounds use lighter-weight bullets and larger caliber rounds use heavier bullets.
LENGTH
Sometimes a cartridge is also designated by its case length. (The case is that empty shell that ejects from the semi-auto pistol after fire a round.)
For instance, that popular 9mm cartridge—the one everyone loves to shoot—is referred to as 9x19.
Nine is the bullet diameter, and 19 is the case length. Both measurements are in millimeters. This common cartridge is also known as 9mm luger and 9mm parabellum.
It can become confusing, as other cartridges are also 9mm in bullet diameter, but the case length is different:
9x18
9mm short
9x21
9x23
The examples above are all very different cartridges.
They are not interchangeable, as their length is different,
but all are designated as 9mm.
