Quick Answer Box
- 5.56/.223 is the right choice for most buyers — cheaper rifle, cheaper ammo, lighter to carry, and capable to 500m.
- .308/7.62x51mm offers significantly more energy, better long-range ballistics, and genuine 800m+ capability — at the cost of a heavier and more expensive platform.
- A .308 AR (AR-10/DPMS-pattern) costs roughly $400–$500 more than a comparable 5.56 AR-15, and ammo costs about twice as much.
- 5.56 barrel life is ~20,000 rounds; .308 barrels last ~8,000–10,000 rounds.
- Pick .308 if you hunt large game at 400+ yards or shoot long-range precision. Pick 5.56 for everything else.
Introduction
The question of 5.56 vs. .308 for an AR-platform rifle really comes down to what you’re actually going to do with it. 5.56 is the right answer for most shooters — it’s more affordable to buy, cheaper to feed, and covers everything from home defense to 500-meter steel with confidence. The .308 earns its place for hunters pushing past 400 yards and precision shooters who need the extra energy and bullet weight that only a larger cartridge can deliver.
A Brief History of Both Cartridges
.308 Winchester / 7.62x51mm NATO
The .308 Winchester was introduced commercially in 1952, developed from experimental military cartridge work that became the 7.62x51mm NATO in 1954. The intent was a more compact replacement for the .30-06 Springfield that offered similar performance with less powder and shorter case length.
The .308 became the dominant long-range precision cartridge for military snipers, competitive shooters, and hunters for decades. It’s chambered in bolt-action precision rifles, semi-auto designated marksman rifles (M110 SASS, HK417), and the whole category of .308 AR-pattern semi-autos we call AR-10s today.
5.56x45mm / .223 Remington
The 5.56x45mm NATO evolved from the .222 Remington, developed in the late 1950s as part of the US military’s move toward a smaller, lighter service cartridge. It was standardized by the US military in 1963 alongside the M16 rifle. The commercial equivalent, .223 Remington, arrived slightly earlier and uses essentially the same case.
The 5.56 was controversial at adoption — smaller and lighter than the .308 it partially replaced in the AR-15/M16 system — but its effectiveness in combat and the logistical advantages of carrying more ammunition have validated the design over six decades of service.
.223 Remington vs. 5.56x45mm — A Critical Safety Note
These are not fully interchangeable in all rifles. A rifle chambered in .223 Remington should not fire 5.56x45mm NATO without checking the manufacturer’s specifications — 5.56 is loaded to higher pressure. A rifle chambered in 5.56 or .223 Wylde can safely fire both .223 Remington and 5.56 NATO. Most quality AR-15s today use 5.56 or .223 Wylde chambers. Check your barrel stamp before loading mil-spec 5.56 in a .223-chambered rifle.
Platform Differences: What the Caliber Choice Actually Costs You
This is where the 5.56 vs. .308 decision has real-world financial implications beyond just ammo.
Rifle Cost
The AR-15 platform in 5.56 is the most mature, mass-produced firearm platform in America. Entry-level quality (S&W M&P Sport II, Ruger AR-556) starts at $600–$700. Mid-tier quality rifles (BCM, Aero Precision complete) run $900–$1,200.
The .308 AR (DPMS-pattern or ArmaLite-pattern) starts around $1,100–$1,200 for a quality entry-level rifle (Aero Precision M5, S&W M&P10). Mid-tier runs $1,300–$1,700.
That’s $400–$600 more just to get on the .308 platform — before you buy optics, ammo, or accessories.
Aftermarket and Component Cost
The AR-15 in 5.56 has the largest aftermarket of any firearm ever made. Triggers, handguards, stocks, barrels, BCGs — hundreds of manufacturers compete, driving prices down. A quality drop-in trigger for an AR-15 runs $100–$250. The same level of component is available for .308 AR but from fewer manufacturers at higher prices. Check out our best AR-15 upgrades under $200 for popular mods that work on either platform.
How Do the Ballistics Actually Compare?
| Metric | 5.56mm 55gr M193 | .308 Win 168gr BTHP |
|---|---|---|
| Muzzle Velocity | 3,240 fps | 2,650 fps |
| Muzzle Energy | 1,282 ft-lbs | 2,620 ft-lbs |
| Velocity at 300 yards | ~2,440 fps | ~2,290 fps |
| Energy at 300 yards | ~727 ft-lbs | ~1,955 ft-lbs |
| Velocity at 500 yards | ~1,900 fps | ~2,060 fps |
| Energy at 500 yards | ~441 ft-lbs | ~1,580 ft-lbs |
| Drop at 500 yards (100yd zero) | ~47″ | ~32″ |
| Recoil (free recoil energy) | ~5 ft-lbs | ~17 ft-lbs |
| Ammo Cost (FMJ) | $0.30–$0.45/rd | $0.50–$0.80/rd |
| Barrel Life (approx) | ~20,000 rounds | ~8,000–10,000 rounds |
The .308’s energy advantage is dramatic — roughly double at every distance. At 500 yards, the .308 carries 1,580 ft-lbs vs. the 5.56’s 441 ft-lbs. That’s the difference between a confident hunting shot on a whitetail and a marginal one.
The .308 also drops less. With a 100-yard zero, the .308 drops about 32 inches at 500 yards vs. 47 inches for the 5.56. Flatter trajectory means less holdover to remember and smaller range estimation errors.
Recoil is the other side of this equation. The .308’s ~17 ft-lbs of free recoil is more than triple the 5.56’s ~5 ft-lbs. This affects how quickly you can shoot accurately in follow-up shots, how fatiguing extended range sessions are, and the tolerance of smaller or more recoil-sensitive shooters.
Effective Range: What “800 Meters” Actually Means
The 5.56mm is effective to approximately 500 meters against point targets in trained hands. This is the military standard, backed by decades of combat data and training. Beyond 500 meters, the 5.56mm is losing energy rapidly and wind drift becomes increasingly difficult to compensate for.
The .308 Winchester extends practical effective range to 800 meters and beyond for precision shooters. The 168gr BTHP has a significantly better ballistic coefficient than the 55gr 5.56 projectile, meaning it retains velocity, energy, and trajectory stability better in the wind.
For deer hunting: a well-placed 5.56 shot at 300 yards with a quality hunting load is effective. At 400 yards, you’re pushing the ethical boundary. At 500 yards, the .308 is the clear choice. For precision steel shooting at 600+ yards, the .308 is noticeably easier to get hits with than the 5.56. See our full breakdown of best AR-10 rifles for .308.
Which Caliber Is Right for Each Use Case?
| Use Case | Best Caliber | Why |
|---|---|---|
| Home Defense | 5.56 | Lower recoil, higher capacity, less overpenetration risk with frangible ammo |
| Deer Hunting (under 300 yds) | Either | Both adequate with proper loads; 5.56 with 77gr OTM is marginal, .308 is comfortable |
| Deer Hunting (300–500 yds) | .308 | Energy advantage becomes significant |
| Long-Range Precision (600+ yds) | .308 or 6.5 CM | Better BC, energy retention, and trajectory at distance |
| General Range Use | 5.56 | Far cheaper per round — enables more practice |
| SHTF / High-Volume Shooting | 5.56 | Cost, weight, and ammo availability all favor 5.56 |
| Designated Marksman Role (to 800m) | .308 | Designed for this; standard military DM cartridge |
| Budget-Conscious First AR | 5.56 | $400–$600 cheaper entry; ammo roughly half the cost |
What About 6.5 Creedmoor as a Third Option?
Worth mentioning: if long-range precision is your primary goal, 6.5 Creedmoor in an AR-10/DPMS-pattern rifle is increasingly compelling. The 6.5 CM’s superior ballistic coefficient means less wind drift and better velocity retention at 800+ yards compared to .308.
The trade-offs: barrel life is shorter (~2,000–3,000 rounds vs. .308’s 8,000–10,000 rounds), and match-grade 6.5 CM ammo runs $1.00–$1.50/round vs. $0.50–$0.80 for .308. For precision rifle competition (PRS, F-Class), 6.5 CM has largely displaced .308. For hunting versatility and budget, .308 still has its place.
FAQ
Can I shoot .308 in an AR-15? No. Standard AR-15 lowers and uppers are not designed for .308 Winchester — the cartridge is too large. You need a .308 AR (DPMS-pattern or ArmaLite-pattern) specifically designed for the larger cartridge. The receiver, bolt, and barrel are all different.
Is .308 too much recoil for a new shooter? Manageable but noticeable. At ~17 ft-lbs of free recoil, a .308 AR is not punishing, but it’s significantly more than a 5.56. Most people can handle it fine. For new shooters who are recoil-sensitive, starting with 5.56 is a better foundation before stepping up to .308.
Which caliber is better for feral hog hunting? Both work. The .308 is overkill for hogs at typical hunting ranges (under 200 yards) but provides excellent terminal performance. The 5.56 in 62gr or heavier hunting loads is effective on hogs under 150 yards. For larger boars or longer shots, the .308 provides a meaningful margin.
Do I need a different scope for a .308 AR vs. a 5.56 AR? The optic itself doesn’t change — any quality scope works on either caliber. You’ll need to zero for the specific caliber and bullet weight, and longer-range reticles (BDC or MRAD) will have different subtension values for .308 vs. 5.56.
What’s the best .308 load for deer hunting? Federal Fusion 165gr and Hornady InterLock 165gr are proven performers at reasonable prices. For premium hunting, Federal Trophy Bonded Bear Claw or Nosler Partition in 165gr or 180gr provide excellent controlled expansion. Any quality 150–180gr bonded hunting bullet in .308 will handle deer cleanly inside 500 yards.
Conclusion
For most shooters, the 5.56 AR-15 is the answer. It’s cheaper to buy, dramatically cheaper to feed, and covers every practical defensive and recreational shooting application with room to spare. The .308 AR earns its place when you genuinely need more energy and range than 5.56 can deliver — deer at 400+ yards, precision steel at 600–800 meters, or dedicated long-range practice. If you’re honest about how you’ll actually use the rifle, the caliber choice mostly makes itself. Our AR-15 Buyer’s Guide is a good next stop if you’re still deciding on a platform.