300 AAC Blackout vs 5.56 NATO: Ballistics, Suppressors, Cost & Best Uses
300 AAC Blackout (300 BLK) and 5.56 NATO are both popular AR-15 calibers, but they serve different purposes. This guide breaks down ballistics, applications, costs, and helps you choose the right caliber for your needs.
300 Blackout vs 5.56: Which AR-15 Caliber is Right for You?
Both 300 AAC Blackout (300 BLK) and 5.56 NATO run in AR-15 platforms, but they're designed for different missions. 5.56 is the military standard optimized for intermediate range with standard barrel lengths. 300 Blackout was designed specifically for short-barreled rifles and suppressor use, offering subsonic capability that 5.56 can't match.
For complete AR-15 optics recommendations, see our Best Red Dot Sights for AR-15 guide.
Quick Comparison Table
| Factor | 300 BLK | 5.56 NATO |
|---|---|---|
| Effective Range | ~200–300 yards typical; some hunting/precision loads can stretch farther (use/target dependent) | ~300–600 yards typical; depends heavily on barrel length, load, and target |
| Suppressor Use | Excellent (subsonic) | Fair (supersonic; much louder than 300 BLK) |
| Barrel Length | Optimized for short barrels (8-10") | Benefits from longer barrels (14.5–20"; velocity-dependent) |
| Energy (Muzzle) | ~1,250–1,500 ft-lbs (supersonic; barrel/load dependent) | ~1,100–1,350 ft-lbs typical (barrel/load dependent; often higher from 18–20") |
| Penetration | Load-dependent; can perform well on intermediate barriers with some supersonic loads | Varies widely by load; FMJ/OTM/bonded differ a lot—barrier performance is load-dependent |
| Ammo Cost | Typically higher (often ~1.5–3× 5.56, market dependent) | Typically lower, widely available |
| Availability | Good | Excellent |
Ballistic Performance
5.56 NATO: Velocity-dependent round that needs barrel length to reach full potential. From a 16\" barrel, 55gr M193 is often around ~3,000–3,200 fps and can fragment at sufficiently high impact velocities (range/barrel/load dependent), but many modern defensive loads are designed to expand or fragment more consistently across a wider velocity window. Short barrels (especially under ~11.5\") reduce velocity, which can reduce effective terminal performance depending on the specific load/design.
300 Blackout: Designed around short barrels. Is less sensitive to short barrels than 5.56; it still loses velocity as barrels get shorter, but generally retains performance better in SBR lengths. Supersonic loads (~2,200 fps with 125gr) can be comparable in energy to 7.62x39 (load/barrel dependent). Subsonic loads (~1,000 fps with 220gr) are much quieter when suppressed, but still not reliably hearing-safe.
Best Use Cases
Choose 300 Blackout if you:
- Run short barrels (8-10.5 inches)
- Use a suppressor regularly
- Want subsonic capability
- Hunt medium game under 200 yards
- Prioritize home defense with suppressor use (overpenetration depends on bullet type/construction)
Choose 5.56 NATO if you:
- Use 14.5\"+ barrels
- Need effective range beyond 300 yards
- Want cheapest ammo and widest availability
- Need consistent barrier performance (choose bonded/barrier loads)
- Shoot high volume
Cost Comparison
5.56 NATO is usually cheaper and easier to buy in bulk. 300 Blackout commonly costs ~1.5–3× more depending on market conditions and whether you're buying supersonic vs subsonic. If you shoot 1,000 rounds per year, that difference can add up quickly.
Frequently Asked Questions
Is 300 Blackout better than 5.56?
Neither is universally better. 300 BLK excels with short barrels and suppressors, especially subsonic. 5.56 has longer effective range and cheaper ammo; barrier/penetration performance depends heavily on the specific load. Choose based on your primary use case.
Can I shoot 300 Blackout in a 5.56 AR-15?
NO! You must swap the barrel (and use correct ammo). Never attempt to fire 300 BLK in a 5.56 barrel—it will cause catastrophic failure. A 300 BLK round can chamber in some 5.56 mags and rifles, which is why labeled mags and strict ammo separation matter. The bolt and lower receiver can be reused. Standard 5.56 magazines often work, but dedicated/labeled 300 BLK magazines are strongly recommended to prevent dangerous mix-ups.
Which is better for home defense?
300 BLK subsonic + suppressor reduces blast/noise, but overpenetration depends heavily on bullet type and construction. Choose purpose-built defensive loads and test/consider your walls/backstops. 5.56 offers wide ammo selection and generally lower recoil/cheaper practice, but performance varies widely by load. Both work; if you're committed to running suppressed, 300 BLK is often the easier path—especially with subsonic.
Is 300 Blackout worth the extra cost?
If you run short barrels (under 10.5") or suppressors regularly, yes. For general purpose use with 16" barrels, 5.56 offers better value and performance.
Bottom Line
For most shooters with 16\" AR-15s, 5.56 NATO is the better choice—it's cheaper, more available, and more effective at typical engagement distances. 300 Blackout shines when you're running short barrels (under 10.5\") or suppressors, where its design advantages become apparent. Both are excellent; your use case determines the winner.