Whether you're new to firearms or just brushing up on the basics, understanding handgun ammunition can be one of the more overwhelming parts of getting started. Between the acronyms, calibers and casing types, it’s easy to feel lost.
Let’s break down the fundamentals of rimfire vs. centerfire ammo, the real definition of caliber and the major types of bullet constructions and acronyms you'll see on shelves.
WHAT DOES CALIBER REALLY MEAN?
“Caliber” gets tossed around a lot, but its meaning depends on context. Technically, it refers to the internal diameter of your gun’s barrel — essentially, how wide the bullet needs to be to fit the proper gun. For example, a 9mm pistol fires bullets that are 9 millimeters in diameter.
But when you’re shopping for ammo, “caliber” becomes more of a shorthand.
“It’s one of the easiest ways to label the type of ammo you need for your firearm,” John said.
Here’s where it gets tricky: bullets with the same diameter can still belong to different calibers.
“.380, 9mm and .38 Super all use the same bullet size but have different case lengths and powder loads,” John explained.
That’s why two boxes of ammo can look nearly identical — but behave very differently.
Rimfire vs. Centerfire
“The majority of ammunition out there is going to be centerfire,” John explained. “That’s where the primer is located in the center of the back of the cartridge.”
On the other hand, rimfire rounds contain the priming compound in the outer rim of the case. Popular examples include .22 Long Rifle, .22 Short and .22 Magnum.
“You’ll notice the rim sticks out from the wall of the case significantly, and that’s where the priming material is located,” John said.
While centerfire is the dominant format for modern handguns, rimfire remains a favorite for training, but outside of that it’s uses are limited.
“Fifty rounds of 9mm might cost you $14, but you can buy 550 rounds of .22 long rifle for like $28,” he added.
That makes rimfire an accessible, low-recoil option for new shooters. However, it’s not ideal for defense if given other options. Centerfire is more powerful and often more reliable in those situations.
Full Metal Jacket, Hollow Point & More
So you’ve picked a caliber. Great! Now what’s with all the confusing letters on the box? Let’s decode the most common ones:
FMJ — Full Metal Jacket
- Encased lead bullet
- Rounded tip matches body
- Target/range use
These are your basic range rounds, made of lead and covered in metal. They are cheap to make and easy to find. But keep in mind — it will go right through your target.
“FMJ can over-penetrate. It’s not ideal for self-defense,” John added.
JHP — Jacketed Hollow Point
- Concave, hollow point
- Expands on impact
- Good for self-defense, home defense and law enforcement
This is what you carry if you’re protecting yourself.
“It expands on impact,” John said. “That slows the bullet down and reduces the chance of it going through and hitting something — or someone — else.”
JHP is ideal for any defense situation.
V-max — Polymer-tipped hollow point
- Specialty round
- Aerodynamic + expanding impact
- Best for hunting medium game animals
This ammunition is a form of a hollow point bullet, but in the hollow point, you’ll find a pointed polymer tip that will push down into the body of the bullet to expand upon impact.
V-MAX bullets are not intended for casual range use due to their higher cost and specialized role. They're designed for hunting and precision shooting, especially for small to medium game.
PSP — Pointed Soft Point
- Exposed lead tip
- Expands on impact
- Common in hunting rounds
These are typically for hunters. The tips of those bullets are not fully encased. They are not in a full metal jacket. Rather, the tips are exposed. This deformation is useful in hunting scenarios, where bullet expansion and energy transfer are important for an ethical and effective shot.
They aren’t as dramatic as a hollow point, but they still do the job.
Bottom Line of Ammo Selection
The world of ammo is bigger than most beginners realize — but that’s part of what makes it fun. Whether you’re plinking with .22 LR or loading up for carry with JHPs, there’s always more to learn, test and explore.
Want to put your knowledge to work? Start by checking your own ammo collection — or visit the Armscor lineup to see how full metal jackets, hollow points and calibers stack up.
