Ammunition & Calibers Guide
14 handgun calibers · 15 rifle calibers · 6 bullet types · storage best practices
Understanding ammunition is foundational to safe, confident firearm ownership. This guide covers everything from cartridge anatomy to caliber selection, bullet construction, reading an ammo box, and proper storage -written for all experience levels.
How Ammunition Works
A complete cartridge (commonly but incorrectly called a "bullet") consists of four fundamental components that work together in a rapid ignition sequence.
Cartridge Anatomy
Case (Casing)
The outer container holding all components together. Typically brass, but also available in steel or aluminum. Extracted and ejected after firing. May be rimmed, semi-rimmed, rimless, rebated rim, or belted.
Primer
A small, pressure-sensitive explosive compound in the cartridge base. When struck by the firing pin, it ignites and sends a flash of hot gas through the flash hole(s) into the powder charge.
Propellant (Powder)
Modern smokeless powder (nitrocellulose-based). When ignited by the primer, it burns rapidly, producing expanding gases that propel the bullet down the barrel. Amount and type determine velocity and pressure.
Bullet (Projectile)
The only component that exits the barrel. The case, primer, and spent powder residue remain behind. Measured by weight in grains (1 grain = 1/7,000 of a pound = 64.79 mg).
The Complete Ignition Sequence
- 1The shooter pulls the trigger, releasing the hammer or striker.
- 2The hammer/striker drives the firing pin forward.
- 3The firing pin strikes the primer cup at the cartridge's base.
- 4The impact crushes the priming compound against the anvil.
- 5The priming compound detonates, generating hot gases and sparks.
- 6Hot gases travel through the flash hole(s) into the powder chamber.
- 7The propellant powder ignites and burns rapidly.
- 8Expanding gases build pressure behind the bullet (10,000-65,000+ psi depending on caliber).
- 9The bullet separates from the case and accelerates down the barrel.
- 10Rifling in the barrel imparts spin, stabilizing the bullet in flight.
- 11The bullet exits the muzzle; the case remains in the chamber.
Centerfire vs. Rimfire
Centerfire
- Separate primer seated in the center of the cartridge base
- Used for the vast majority of handgun and rifle calibers
- Cases can be reloaded (reused) multiple times
- More reliable ignition than rimfire
- Available from .17 caliber through .50+ caliber
Rimfire
- Priming compound distributed around the entire rim
- Primarily for .22 LR, .22 WMR, .17 HMR, .17 HM2
- Cases CANNOT be reloaded -rim is deformed when fired
- Less expensive to manufacture than centerfire
- Limited to lower-pressure cartridges (thin rim construction)
Primer Types: Boxer vs. Berdan
Boxer Primers
Edward Mounier Boxer, 1860s
- Self-contained unit with the anvil built into the primer
- Single flash hole -easy to decap and reload
- Standard for all U.S.-manufactured civilian factory ammo
- Four standardized sizes (Small/Large Pistol, Small/Large Rifle) plus magnum variants
Berdan Primers
Hiram Berdan, 1860s
- Anvil is part of the cartridge case, not the primer
- Two or three flash holes around the anvil
- Common in military surplus and non-U.S. manufactured ammo
- Very difficult to reload -primer sizes not standardized
Practical note: There is no performance difference between Boxer and Berdan primed ammunition in terms of velocity, energy, or accuracy. The distinction matters primarily to reloaders (Boxer is strongly preferred) and to shooters buying surplus ammunition (often Berdan-primed).
Handgun Calibers
Fourteen handgun calibers from the ubiquitous .22 LR to the earth-shaking .500 S&W Magnum. Each card shows key specs, typical cost, and whether the caliber is appropriate for beginners.
.22 LR
Beginner FriendlyRimfire · Introduced 1887
Common Uses
Training, target shooting, plinking, small-game hunting, competition
The most widely sold ammunition in the world. The go-to recommendation for new shooters due to minimal recoil, low noise, and extremely low cost.
For new shooters: The ideal starting caliber for all new shooters.
.25 ACP
ExperiencedCenterfire, semi-rimmed · Introduced 1905
Common Uses
Deep concealment pocket pistols, backup firearms
Designed by John Browning as the smallest centerfire pistol cartridge. Largely considered inadequate for self-defense by modern standards.
For new shooters: Low recoil but very limited availability and utility.
.32 ACP
ExperiencedCenterfire, semi-rimmed · Introduced 1899
Common Uses
Compact pocket pistols, concealed carry, collecting
Once the standard military sidearm cartridge for many European nations. Experiencing a modern resurgence in ultra-compact pistols.
For new shooters: Manageable recoil but limited modern firearm options.
.380 ACP
Beginner FriendlyCenterfire, rimless · Introduced 1908
Common Uses
Self-defense in compact/subcompact pistols, concealed carry
Also known as 9mm Kurz/Short. The entry-level threshold for what experts consider adequate self-defense performance with modern JHP ammunition.
For new shooters: Excellent step up from .22 LR for those ready for more.
9mm Luger
Beginner FriendlyCenterfire, rimless · Introduced 1901
Common Uses
Self-defense, law enforcement, military, competition, target shooting
The most popular handgun cartridge in the world. Standard issue for the vast majority of law enforcement and military forces globally. Advances in JHP bullet technology have closed the gap with larger calibers.
For new shooters: The gold standard. Ideal balance of capacity, recoil, and effectiveness.
.38 Special
Beginner FriendlyCenterfire, rimmed · Introduced 1898
Common Uses
Revolver self-defense, target shooting, training
Despite the ".38" name, the actual bullet diameter is .357 inches. Any .357 Magnum revolver can safely fire .38 Special ammunition. For decades, the standard law enforcement cartridge.
For new shooters: One of the gentlest centerfire cartridges. Great for revolver beginners.
.357 Magnum
ExperiencedCenterfire, rimmed · Introduced 1935
Common Uses
Self-defense, hunting, wilderness carry, competition
Revolvers chambered in .357 Magnum can also fire .38 Special -practice with milder .38 and carry .357 Magnum. Case identical to .38 Special but slightly longer to prevent dangerous mix-ups.
For new shooters: Significant recoil and muzzle blast. Master .38 Special first.
.40 S&W
ExperiencedCenterfire, rimless · Introduced 1990
Common Uses
Law enforcement, self-defense, competition
Born from the FBI's search after the 1986 Miami shootout. Essentially a shortened 10mm Auto. Many agencies have since transitioned back to 9mm. Described as "snappy" recoil.
For new shooters: Snappy recoil can be challenging for new shooters.
10mm Auto
ExperiencedCenterfire, rimless · Introduced 1983
Common Uses
Hunting, wilderness/bear defense, self-defense, competition
Full-power 10mm loads are substantially more powerful than .40 S&W. Experiencing a significant resurgence for outdoors/woods carry. Capable of taking deer and even bear.
For new shooters: Too much recoil for beginners. Build up to this one.
.45 ACP
ExperiencedCenterfire, rimless · Introduced 1904
Common Uses
Self-defense, competition, military heritage
Standard US sidearm cartridge from 1911-1985. Naturally subsonic and suppressor-friendly. Recoil described as a slow, rolling "push" rather than a sharp snap. Over 120 years old and still immensely popular.
For new shooters: Manageable "push" recoil, but the large grip size can be challenging for smaller hands.
.44 Special / .44 Magnum
ExperiencedCenterfire, rimmed · Introduced 1907 / 1955
Common Uses
.44 Spl: target, self-defense. .44 Mag: hunting, wilderness defense
.44 Special is the parent case of .44 Magnum. Fire .44 Special in any .44 Magnum revolver. Made famous by the "Dirty Harry" films. Despite the ".44" name, actual bullet diameter is .429 inches.
For new shooters: .44 Special is manageable. .44 Magnum has extreme recoil and muzzle blast.
.357 SIG
ExperiencedCenterfire, rimless, bottlenecked · Introduced 1994
Common Uses
Law enforcement (Secret Service, Texas DPS), self-defense
Based on a necked-down 10mm Auto case. Replicates .357 Magnum ballistics in a semi-auto platform. The bottleneck design provides exceptionally reliable feeding.
For new shooters: Sharp recoil and expensive ammo make this a poor beginner choice.
5.7x28mm
ExperiencedCenterfire, rimless, bottlenecked · Introduced 1990
Common Uses
Military/LE (NATO PDW), self-defense, competition
Designed for the FN P90 and FN Five-seven. Approximately 30% less recoil than 9mm. Extremely flat trajectory. Achieved NATO standardization in 2021.
For new shooters: Very low recoil but expensive ammo and limited firearm options.
.500 S&W Magnum
ExperiencedCenterfire, semi-rimmed · Introduced 2003
Common Uses
Hunting all North American big game, handgun hunting at extended range
The most powerful production handgun cartridge. The S&W Model 500 revolver weighs 3.5-5.1 lbs to help mitigate recoil. NOT suitable for beginners.
For new shooters: Absolutely not for beginners. Extreme recoil requires substantial experience.
CRITICAL SAFETY WARNING: .223 Remington vs. 5.56x45mm NATO
These two cartridges are closely related but NOT fully interchangeable. The most important difference is the chamber dimensions, not just the pressure rating.
A 5.56 NATO chamber has a 0.125" longer throat (leade) than a .223 Remington chamber. This longer throat allows more space for the bullet before engaging the rifling, resulting in lower pressure.
The Solution: The .223 Wylde chamber (created by Bill Wylde) is a hybrid design that safely fires both .223 Remington and 5.56 NATO ammunition. This is the most common chamber for modern AR-15 rifles. Always check your firearm's markings to determine which chamber it has.
.300 BLK / 5.56 NATO Cross-Chambering Danger
A .300 AAC Blackout round can physically chamber in a 5.56/.223 barrel. Firing it will cause catastrophic barrel obstruction and failure. If you own firearms in both calibers, always clearly label your magazines and keep ammunition separated.
Rifle Calibers
Fifteen rifle calibers from the gentle .22 LR to the extreme-long-range .338 Lapua Magnum. Includes historic military cartridges, modern precision rounds, and straight-wall hunting options.
.22 LR (Rifle)
Beginner FriendlyRimfire · Introduced 1887
Common Uses
Small-game hunting, plinking, training, competitive shooting (NRA Smallbore, Olympic Biathlon)
The single most popular caliber in the world by total rounds sold annually. Higher velocity from rifle-length barrels than from pistols. The ideal training cartridge for rifles.
For new shooters: The perfect first rifle cartridge. Virtually no recoil.
.223 Rem / 5.56 NATO
Beginner FriendlyCenterfire, rimless, bottlenecked · Introduced 1964 / 1961
Common Uses
Target shooting, home defense, varmint hunting, military/LE, competition
CRITICAL CHAMBER DIFFERENCE -see safety warning below. 5.56 NATO has a longer throat than .223 Rem. The .223 Wylde chamber safely handles both. Always check your firearm markings.
For new shooters: Low recoil and widely available. Verify your chamber type first!
.300 AAC Blackout
ExperiencedCenterfire, rimless, bottlenecked · Introduced 2011
Common Uses
Home defense, hunting, suppressed shooting, military/LE
Uses standard AR-15 magazines and components -only the barrel changes. WARNING: 300 BLK can physically chamber in a 5.56 barrel. Firing it WILL cause catastrophic failure. Always label magazines.
For new shooters: Versatile but requires careful magazine discipline to avoid dangerous mix-ups with 5.56.
6.5mm Creedmoor
ExperiencedCenterfire, rimless, bottlenecked · Introduced 2007
Common Uses
Long-range target/competition, medium-game hunting, precision rifle matches (PRS)
Superior ballistic coefficients to .308 Win. SOCOM testing showed it doubled hit probability at 1,000 meters and reduced wind drift by a third vs 7.62 NATO. Rapidly becoming one of the most popular rifle cartridges.
For new shooters: Moderate recoil but expensive ammo. Better after mastering .223.
.308 Win / 7.62x51 NATO
ExperiencedCenterfire, rimless, bottlenecked · Introduced 1952 / 1954
Common Uses
Hunting, military/LE sniping, precision shooting, competition -the "do everything" rifle cartridge
.308 Win has a slightly higher max pressure (62,000 vs 60,000 psi). Most modern rifles handle both safely, but match ammo to your chamber markings. Used in the M14 and M60.
For new shooters: More recoil than .223 but extremely versatile. Good second rifle caliber.
.30-06 Springfield
ExperiencedCenterfire, rimless, bottlenecked · Introduced 1906
Common Uses
Hunting (all North American big game), military heritage, competition
Standard U.S. military cartridge from 1906-1954. Used in the M1903 Springfield and M1 Garand. Offers slightly more energy than .308 Win due to larger case capacity. The #1 deer cartridge historically in the United States.
For new shooters: Significant recoil. Not recommended as a first rifle cartridge.
.30-30 Winchester
ExperiencedCenterfire, rimmed, bottlenecked · Introduced 1895
Common Uses
Deer hunting, brush hunting, lever-action enthusiasts
America's first sporting cartridge with smokeless powder. Originally "30-30" = 30 grains of powder. Effective range 200-250 yards. Quintessential lever-action deer cartridge (Winchester 94, Marlin 336).
For new shooters: Moderate recoil in a lever-action. A classic choice after mastering fundamentals.
.45-70 Government
ExperiencedCenterfire, rimmed, straight-walled · Introduced 1873
Common Uses
Big game hunting (moose, bear, bison), cowboy action shooting
Named for its original loading: .45-caliber bullet with 70 grains of black powder. Three load levels: "Trapdoor" (lowest), "Lever-action" (medium), "Ruger/TC" (highest). Match load level to your rifle's strength rating.
For new shooters: Very heavy recoil. For experienced shooters only.
7.62x39mm
ExperiencedCenterfire, rimless, bottlenecked · Introduced ~1944 (WWII era)
Common Uses
Sporting/hunting, recreational shooting, military heritage (AK-47, SKS)
Made famous by the AK-47. One of the most widely produced cartridges in history. Effective range ~300 meters. Often available as inexpensive steel-cased, Berdan-primed surplus (not reloadable).
For new shooters: Moderate recoil with affordable ammo. Check if your range allows steel-cased ammo.
5.45x39mm
ExperiencedCenterfire, rimless, bottlenecked · Introduced 1974
Common Uses
Sporting, military heritage (AK-74)
Soviet response to the 5.56 NATO concept. Supply has become restricted due to import bans on Russian ammunition (7N6 surplus banned 2014; broader bans in 2021).
For new shooters: Low recoil but very limited ammo availability in the U.S.
.300 Winchester Magnum
ExperiencedCenterfire, belted magnum, bottlenecked · Introduced 1963
Common Uses
Long-range hunting (elk, moose, African plains game), military sniping
Extremely popular for western big-game hunting. Offers significantly more energy than .308 Win at all ranges. Effective for hunting to 500+ yards.
For new shooters: Heavy recoil and expensive. For experienced rifle shooters.
.338 Lapua Magnum
ExperiencedCenterfire, rimless, bottlenecked · Introduced ~1989
Common Uses
Military sniping (extreme long range), extreme long-range target shooting, dangerous game
Effective range exceeds 1,500 meters. Produces approximately 40% more muzzle energy than .300 Win Mag. Rifles and ammo are expensive -a specialty cartridge.
For new shooters: Requires a muzzle brake and substantial experience. Not a beginner caliber.
6.5mm Grendel
ExperiencedCenterfire, rimless, bottlenecked · Introduced ~2003
Common Uses
Medium-game hunting, target shooting, long-range AR-15 use
Designed for the AR-15 to surpass 5.56 NATO at 200-800 yards. The 123 gr load maintains supersonic velocity to 1,000 yards. Requires a non-standard bolt face for AR-15.
For new shooters: Low recoil but niche platform requirements. Better as a second caliber.
.350 Legend
Beginner FriendlyCenterfire, rimless, straight-walled · Introduced 2019
Common Uses
Deer hunting (especially in straight-wall-only states), home defense, target shooting
Designed for states that restrict deer hunting to straight-walled cartridges (Michigan, Ohio, Indiana, Iowa). Uses AR-15 platform with only a barrel change. Max effective range ~250 yards.
For new shooters: Low recoil for a deer cartridge. Good first hunting rifle option.
.450 Bushmaster
ExperiencedCenterfire, rebated rim, straight-walled · Introduced ~2000s
Common Uses
Deer and bear hunting in straight-wall states, hog hunting, medium-to-large game
Born from Jeff Cooper's "Thumper" concept -a large-bore AR cartridge for one-shot big-game kills at 250 yards. Hits substantially harder than .350 Legend with significantly more recoil. Most effective inside 200 yards.
For new shooters: Heavy recoil. Consider .350 Legend as the gentler alternative.
Bullet Types
Different bullet constructions serve different purposes. Choosing the right type for your application matters for both safety and effectiveness.
Full Metal Jacket
FMJA lead core completely encased in a harder metal jacket (usually copper). Also called "ball" ammunition. Does not expand on impact; tends to penetrate deeply.
Jacketed Hollow Point
JHPA lead core partially encased in a copper jacket with a hollow cavity in the nose. Upon impact, hydraulic pressure forces the cavity to expand ("mushroom"), increasing diameter.
Soft Point
SPAlmost fully jacketed but with the lead core exposed at the tip. The exposed lead initiates controlled expansion -slower than JHP but with deeper penetration.
Frangible
FRANGMade from compressed metallic powder (copper, tin) sintered together. Designed to disintegrate upon hitting hard surfaces, preventing ricochets. Lead-free.
Wadcutter
WC / SWCA flat-faced bullet that sits flush with the case mouth. Cuts clean, round holes in paper targets. Low velocity, low recoil. Primarily seen in .38 Special revolver loads.
Bonded
BONDEDThe lead core is chemically or mechanically bonded to the copper jacket. Core and jacket stay together during expansion, preventing separation through barriers.
+P and +P+ Ammunition
+P (Plus P)
Ammunition loaded to produce higher internal pressure than standard, resulting in higher velocity and energy. SAAMI publishes official +P specifications.
Example: Standard 9mm = 35,000 psi max. 9mm +P = 38,500 psi max.
Only use in firearms explicitly rated for +P. Increases firearm wear.
+P+ (Plus P Plus)
Loaded even hotter than +P, exceeding SAAMI +P specs. +P+ is NOT a SAAMI-standardized designation. Some manufacturers use it for loads that exceed +P but remain below proof-load pressures.
Only use in firearms specifically rated for +P+ by the manufacturer. Typically reserved for law enforcement duty ammo. More accelerated wear.
Case Materials: Brass vs. Steel vs. Aluminum
Brass Case
Pros
- + Best gas seal -expands under pressure, contracts for smooth extraction
- + Most reliable and accurate
- + Corrosion resistant
- + Reloadable multiple times
Cons
- - Most expensive case material
Best for: All applications -the gold standard
Steel Case
Pros
- + 20-30% cheaper than brass
- + Functional for training and high-volume shooting
Cons
- - Harder on extractors and chambers over time
- - Does not expand/contract as well as brass
- - Not reloadable
- - Some ranges prohibit it
Best for: Budget range training where round count matters most
Aluminum Case
Pros
- + Lighter than brass
- + Cheaper than brass
- + Adequate for training
Cons
- - Softer than brass -potentially more wear on feed ramps
- - Not reloadable (cases crack when reformed)
- - Some ranges prohibit it
Best for: Budget training ammo; indoor ranges where steel is prohibited
Reading an Ammo Box
Understanding the numbers and markings on ammunition packaging is an essential skill. Here is what every marking means.
Centerfire Handgun / Rifle Box Labels
Caliber Designation
The most prominent marking. Must match your firearm exactly. Examples: "9mm Luger," ".45 ACP," ".223 Remington," "5.56x45mm NATO"
Grain Weight (gr)
Weight of the bullet only (not the entire cartridge). 1 grain = 1/7,000 lb. Lighter = higher velocity, flatter trajectory. Heavier = more energy, deeper penetration.
Bullet Type
FMJ (range), JHP (defense), SP (hunting), BTHP (match), OTM (precision), TSX (monolithic copper), V-Max (varmint).
Velocity (fps)
Feet per second at the muzzle. Higher fps = flatter trajectory. Listed on many boxes, especially hunting and defensive ammo.
Energy (ft-lbs)
Kinetic energy at the muzzle in foot-pounds. Indicates the bullet's striking force.
Round Count
Number of cartridges in the box. Common counts: 20 (rifle), 25 (shotgun), 50 (handgun), or bulk quantities.
Manufacturer & Product Line
Brand and product name, e.g., "Federal Premium HST," "Hornady Critical Defense," "Winchester White Box."
Warnings & Markings
+P or +P+ designations, "For Law Enforcement Only" (some loads), temperature warnings, and other safety notices.
Shotgun Shell Box Labels
Shotshell boxes contain additional unique information beyond what you'd find on centerfire handgun or rifle ammunition.
Gauge
Must match your shotgun. Examples: "12 Gauge," "20 Gauge," ".410 Bore." Smaller gauge number = larger bore diameter.
Shell Length
The fired length of the shell. Must not exceed your gun's chamber length. Examples: "2-3/4 in," "3 in," "3-1/2 in."
Shot Size
Size of the pellets. Smaller numbers = bigger pellets. Examples: "#8 Shot" (small, target), "#00 Buckshot" (large, defense), "Slug" (single projectile).
Shot Weight & Material
Total pellet weight in ounces (e.g., "1-1/8 oz"). Material matters legally -waterfowl areas often require non-lead (steel, bismuth, tungsten).
Velocity (fps)
Speed at the muzzle. Higher velocity = more recoil. Some boxes list velocity alongside dram equivalent.
Dram Equivalent
An archaic measurement from the blackpowder era comparing velocity to an equivalent blackpowder charge. Higher = faster = more recoil. Many modern boxes now list fps instead.
Understanding Grain Weight
"Grain" (abbreviated "gr") measures the weight of the bullet (projectile only). One grain equals 1/7,000 of a pound or about 65 milligrams. A 124 gr 9mm bullet weighs about 8 grams. Lighter bullets typically fly faster with less recoil; heavier bullets carry more momentum and penetrate deeper. Neither is inherently "better" -it depends on your intended use.
Ammunition Storage
Proper storage ensures your ammunition remains reliable for years or even decades. Moisture and heat are ammunition's greatest enemies.
Temperature
- Ideal: 55-85 deg F (SAAMI); 50-70 deg F optimal
- Avoid: Prolonged temps above 150 deg F (degrades propellant)
- Avoid: Extreme swings (cause condensation)
- Do NOT store long-term in vehicles -summer interiors exceed 150 deg F
Humidity
- Target: Below 50% relative humidity
- Moisture causes rust, corrosion, primer degradation, and can make propellant ineffective
- Mitigation: Use silica gel desiccant packs; use a dehumidifier in your storage area
Shelf Life
- Modern factory: 10-15 years minimum; 20-50+ years under ideal conditions
- Military surplus: Often 50+ years when sealed (WWII .30-06 still fires)
- Signs of degraded ammo: green/white corrosion, dented cases, discolored primers, loose bullets, unusual smell
Storage Containers
Military Ammo Cans
GI .30-cal and .50-cal ammo cans with rubber gasket seals. Waterproof, airtight, durable, and stackable.
Plastic Ammo Cans
Purpose-built plastic containers (MTM, Plano) with gasket seals. Lighter than metal, still protective.
Original Packaging + Container
Manufacturer's packaging stored inside a sealed outer container. Better than packaging alone.
Cardboard / Loose
Cardboard absorbs moisture. Loose ammunition or ziplock bags are not airtight. Avoid for long-term storage.
10 Best Practices
Store Off the Ground
Place on shelves or pallets to prevent moisture absorption from concrete floors.
Include Desiccant
Silica gel packs inside sealed containers absorb residual moisture.
Label Everything
Caliber, quantity, purchase date, and load type on every container.
Rotate Stock (FIFO)
Use the oldest ammunition first -first in, first out.
Keep Away from Solvents
Petroleum products can degrade primers and case sealant.
Separate from Firearms
When required by law or for safety with children in the home.
Inspect Periodically
Check for corrosion (green/white on brass), moisture intrusion, or seal failure.
Climate-Controlled Indoor Storage
Always superior to garage, shed, or attic storage.
Lock Your Storage
If children or unauthorized persons have access to the area.
Keep in Original Boxes
Prevents cartridges from banging together and damaging bullet tips or primers.
Safety First, Always
Always use ammunition that exactly matches your firearm's chamber markings. Never use damaged, corroded, or reloaded ammunition of unknown origin. If you are ever uncertain about whether a cartridge is safe to fire in your firearm, ask a qualified instructor or gunsmith.
Ready to Experience Different Calibers?
Schedule a familiarization course and shoot multiple calibers in a supportive, low-pressure environment. Find what works for you before you buy.