You’re posted on a fenceline in the Montana breaks, coyote trotting broadside at 350 yards. Do you send a .223 Remington match round for a precise vital hit—or drop the hammer on a 5.56 NATO green tip built to push through brush and bone?

To the untrained eye, .223 Remington and 5.56 NATO look identical. Same case length. Same shoulder. Same diameter. But inside the chamber and behind the pressure curve, they behave like quite different cartridges. One is the civilian precision staple that launched the AR-15 revolution. The other is the military-spec workhorse engineered for reliability under chaos.

After swapping uppers and setups, burning through ammo cans on prairie dog towns, and zeroing rifles from Idaho benches to desert blinds, here’s the definitive breakdown—clear, factual, and field-proven.

.223 Remington vs 5.56 NATO: Brass Tacks

(Representative values; chamber and manufacturer variances apply.)

Category	.223 Remington	5.56 NATO	Edge
Max Pressure	55,000 PSI (SAAMI)	Higher NATO EPVAT pressures	5.56
Chamber Leade	Short (.075") for accuracy	Long (.162–.200") for reliability	Tie (purpose- dependent)
Recoil	~4 ft-lbs	~4.5 ft-lbs	.223
Effective Range	~400 yards	~500 yards	5.56
Terminal Behavior	More fragmentation potential	Better penetration through barriers	Tie (application- dependent)
Bulk Ammo Cost	~$0.30–$0.60	~$0.40–$0.70	.223
Reloading Ease	Easier brass, no crimps	Crimped, staked primers	.223
AR Platform Fit	Excellent for precision builds	Mil-spec reliability in adverse conditions	Tie

Pressure, Chambers & Safety: What You Can and Cannot Shoot   

This is a point of confusion for many shooters, specifically the uninitiated. Additionally, this is also where safety matters.

Pressure Differences

Different test methods mean you cannot directly compare the PSI numbers, but 5.56 is consistently the higher-pressure loading.

•.223 Remington is held to SAAMI 55,000 PSI.

•5.56 NATO is measured under NATO EPVAT, not SAAMI, and typically runs hotter.  

Put plainly, shooters with AR-15s and other firearms with either 5.56 or .223 Wylde chambers can utilize either cartridge. This is to say that America’s most popular rifle essentially can utilize 5.56 and .223 ammo interchangeably. Shooters can take advantage of this interchangeability as 5.56 and .223 Wylde chambers are built to withstand the pressures of .223 and 5.56 ammo alike. This allows shooters of such firearms to take advantage of a wide variety of ammunition to feed their rifle of choice. We will expand more on chambers themselves and their relationship with ammunition coming up.

Why the Chamber Matters   

The biggest difference isn’t the ammo—it’s the chamber throat (leade). 

.223 Remington Chamber   

•Shorter, tighter throat

•Increased accuracy potential

•Not designed for high-pressure NATO rounds 

5.56 NATO Chamber   

•Longer throat

•Reduces initial pressure spike

•Allows safe use of hotter NATO rounds 

The Critical Rule   

Never fire 5.56 NATO in a .223-only chamber. 

Why?   

•The shorter .223 throat increases pressure

•5.56 ammo already runs hot

•Combined → Potential overpressure event 

Brass flow, popped primers, stuck cases… or worse.

Safe Combinations  

For your reference, here is a quick guide outlining the safe combinations regarding the two calibers and potential chambers one will likely encounter in the wild.

Chamber	Safe With	Unsafe With
.223 Remington	.223	5.56 NATO
5.56 NATO	.223 & 5.56	—
.223 Wylde	.223 & 5.56	—

Put plainly, as long as you stick to this chart, you should be good to go as far as ensuring you are using the right caliber(s) for your firearm.

The .223 Wylde Chamber: The Smart Middle Ground   

Bill Wylde engineered a hybrid chamber that:

•Uses a tighter .223 throat for accuracy

•Keeps the longer 5.56 freebore for safe NATO pressures 

Result: 

•Sub-MOA potential with match .223

•100% safe with 5.56 M193/M855

•Ideal for shooters running mixed ammo 

If you only want one AR upper?

Get a .223 Wylde chambered barrel.

Recoil & Shootability: Lightweights With Big   

Range   

Both rounds are soft shooters. In a 7 lb rifle: 

•.223 Remington: ~4 ft-lbs

•5.56 NATO: ~4.5 ft-lbs 

You can shoot both all day without fatigue.

Practical Differences   

•.223 feels smoother, especially subsonic or lightly loaded match rounds.

•5.56 has slightly more impulse, noticeable mostly in rapid strings or full-auto platforms. 

Barrel length tip: A 16" mid-length gas system noticeably softens recoil in both calibers.

Ballistics & Effective Range: Speed vs. Versatility 

Both cartridges push 55–77 grain bullets at speeds north of 2,800–3,200 FPS

.223 Remington   

•Optimized for accuracy and consistency 

•Slightly faster with lighter bullets

•Less wind-resistant than 5.56 M855 or Mk 262

5.56 NATO   

•Uses heavier charges and higher pressure 

•62–77 grain loads maintain energy farther

•Better performance beyond 400 yards 

Rule of Thumb:   

•Under 300 yards: Both perform almost identically

•300–500 yards: 5.56 NATO has the edge

Real World Applications  

Hunting Applications   

Varmints (Prairie dogs, foxes)   

✔ .223 Remington

Explosive fragmentation with V-MAX, TNT, or ballistic tips.

Coyotes   

✔ Both, but 5.56 M855 performs better through brush.

Hogs   

✔ 5.56 NATO

Better penetration and energy retention.

Self-Defense Applications  

Home Defense   

✔ .223 Remington with soft points or frangibles

Less barrier penetration reduces collateral risk.

Reloading: The Cost Cutter’s Playground   

.223 Remington Brass   

•Abundant

•Easy to resize

•No crimped primers

•Can survive ~10–20 reload cycles 

5.56 NATO Brass   

•Crimped primer pockets (needs swaging)/staked primers take more effort to remove

•Slightly tougher brass

•Nearly unlimited supply from surplus sources 

Reloading either round can drop your cost to ~$0.20–$0.28 per shot depending on projectile choice.

Representative Ballistics Data (20" Barrels)  

.223 Remington   

Bullet	MV (FPS)	ME (ft-lbs)	Drop @200	Drop @300	Energy @400
55 gr FMJ	3240	1282	-2"	-10"	~850
62 gr SP	3000	1240	-3"	-12"	~800
77 gr OTM	2750	1290	-4"	-15"	~750

5.56 NATO   

Bullet	MV (FPS)	ME (ft-lbs)	Drop @200	Drop @300	Energy @400
55 gr M193	3160	1218	-2.5"	-11"	~820
62 gr M855	3100	1325	-3"	-13"	~900
77 gr Mk 262	2750	1292	-4.5"	-18"	~780

 

Bottom Line: Which Should You Choose?   

Choose .223 Remington if you want: 

•Maximum accuracy

•Cheapest training ammo

•Varmint and predator consistency

•Ideal performance from AR-15 precision builds 

Choose 5.56 NATO if you want: 

•Mil-spec reliability

•Better performance through brush & barriers

•Longer effective range

•A rifle that can handle both 5.56 and .223 safely

Final Take   

If you’re shooting varmints, predators, or want the lowest recoil and best accuracy per dollar, .223 Remington is your rifle’s best friend. If your AR-15 needs to be rugged, barrier-capable, and versatile from 0–500 yards, 5.56 NATO earns its combat pedigree. Whichever direction you go, True Shot Ammo has bulk .223, premium 5.56, match loads, and defensive rounds ready to ship fast. 

👉 Visit TrueShotAmmo.com and get the right load for your next pull of the trigger.