The firearms world has no shortage of “next big thing” calibers—but every so often, a new round genuinely changes the landscape. In recent years, .338 ARC (Advanced Rifle Cartridge) and .400 Legend have become two of the most talked-about options for hunters and AR-platform shooters looking for optimized performance.

Though they serve different purposes, both cartridges are legal in most hunting states, both fit modern sporting rifle platforms, and both deliver impressive energy on game.

But the question remains:
Between .338 ARC and .400 Legend, who’s the winner?

This breakdown covers ballistics, recoil, purpose, AR-platform compatibility, barrel length recommendations, and real-world use cases—plus internal links to top-performing Moriarti Arms uppers.

.338 ARC vs .400 Legend — Ballistics, Use Cases & Optimal Barrel Lengths

.338 ARC vs .400 Legend — Ballistics, Use Cases & Optimal Barrel Lengths

Developed by Hornady, .338 ARC is a high-BC, long-range hunting and precision cartridge designed specifically for the AR-15 platform—yes, AR-15, not AR-10.

It builds on the success of 6mm/6.5 ARC but offers deeper penetration and heavier bullet options. This makes it ideal for medium to large game at extended distances.

Typical Loads:

• 200–225-grain bullets

• High BC projectiles

• 2400–2600 fps depending on barrel length

Platform: AR-15
Comparable to: 8.6 Blackout (lighter), .308 Win (lighter recoil), 350 Legend (longer range), 6.5 Grendel (more punch)

.338 ARC vs .400 Legend — Ballistics, Use Cases & Optimal Barrel Lengths

Released by Winchester in 2023, the .400 Legend is a straight-wall cartridge designed for states requiring straight-wall hunting rounds such as Ohio, Indiana, Iowa, Michigan, and parts of Illinois.

It delivers excellent terminal performance on deer at short-to-mid-range distances and fits beautifully into AR-platform builds.

Typical Loads:

• 190–215-grain bullets

• 2150–2350 fps

• Low recoil

Platform: AR-15
Comparable to: 450 Bushmaster (lighter recoil), 350 Legend (heavier), .30-30 (similar energy)

.338 ARC vs .400 Legend — Ballistics, Use Cases & Optimal Barrel Lengths

.338 ARC vs .400 Legend — Ballistics, Use Cases & Optimal Barrel Lengths

The .338 ARC was born for long-range, high-energy performance. With high-BC bullets exceeding .300+ G1 values and pushing nearly 2600 fps from a 18-inch barrel, it's capable of delivering:

• Flat trajectory

• Deep penetration

• Strong energy retention past 500 yards

It dramatically outperforms the .400 Legend beyond 250 yards.
If you're hunting elk, mule deer, hogs, or black bear, the .338 ARC is a superior choice.

Recommended Upper:
Moriarti AR-15 16" .338 ARC Upper Assembly delivers competition-grade accuracy with proven reliability.

.338 ARC vs .400 Legend — Ballistics, Use Cases & Optimal Barrel Lengths

The .400 Legend was engineered to replace older straight-wall options like .450 Bushmaster, while offering:

• 30% less recoil

• Faster follow-up shots

• Better accuracy

• Better ammo availability

• Legal compliance in straight-wall states

It shines inside 250 yards, which covers nearly every whitetail hunt in the Midwest.

Recommended Upper:
Moriarti AR-15 .400 Legend 16" M-LOK Upper is lightweight, accurate, and extremely effective for woods and field hunting.

.338 ARC vs .400 Legend — Ballistics, Use Cases & Optimal Barrel Lengths

If recoil matters (or you want fast follow-up shots), the difference is huge:

• .338 ARC – similar to 6.5 Grendel or light .308 Win recoil

• .400 Legend – like shooting a .350 Legend or 20-gauge slug

Inside an AR-15 gas system with a good brake, .400 Legend is very comfortable.

Winner for recoil-sensitive shooters or new hunters: .400 Legend

.338 ARC vs .400 Legend — Ballistics, Use Cases & Optimal Barrel Lengths

As of late 2025:

.338 ARC Ammo

• Medium availability

• Growing rapidly

• $35–$55 per box

• Mostly premium hunting loads

.400 Legend Ammo

• Widely available

• $22–$35 per box

• Numerous hunting-specific loads

Winner for affordability: .400 Legend

.338 ARC vs .400 Legend — Ballistics, Use Cases & Optimal Barrel Lengths

This is where many shooters get it wrong.

.338 ARC vs .400 Legend — Ballistics, Use Cases & Optimal Barrel Lengths

20–22 inches
Why?

• Higher velocity matters for long-range expansion

• ARC burns slower powder

• 22" gives nearly 150–200 fps more than 16"

.338 ARC vs .400 Legend — Ballistics, Use Cases & Optimal Barrel Lengths

16–18 inches
Why?

• Straight-wall efficiency peaks in shorter barrels

• Minimal velocity gain beyond 18"

• 16" stays maneuverable for tree stands, blinds, and brush

.338 ARC vs .400 Legend — Ballistics, Use Cases & Optimal Barrel Lengths

.338 ARC Accuracy

The ARC’s ability to accommodate high-BC bullets gives it a precision advantage. It can easily produce 1 MOA or better at 100 yards with match or hunting ammo.

.400 Legend Accuracy

Being a straight-wall cartridge, its effective accuracy envelope is shorter. Inside 200 yards, 1.5–2 MOA is typical, which is plenty for deer.

Winner in precision: .338 ARC

.338 ARC vs .400 Legend — Ballistics, Use Cases & Optimal Barrel Lengths

Both work extremely well, depending on where you hunt.

.338 ARC vs .400 Legend — Ballistics, Use Cases & Optimal Barrel Lengths

You want long-range capability
You're hunting elk, bear, mule deer, or hogs
You want a cartridge that punches like a lightweight .308
You want a ballistically impressive AR-15 caliber
You like premium projectiles

.338 ARC vs .400 Legend — Ballistics, Use Cases & Optimal Barrel Lengths

You live in a straight-wall–restricted state
You want light recoil & You want affordable ammunition

Your shots are inside 200–250 yards
You want the most efficient whitetail woods cartridge

.338 ARC vs .400 Legend — Ballistics, Use Cases & Optimal Barrel Lengths

Winner for Long-Range:

.338 ARC

Winner for Whitetails in Straight-Wall States:

.400 Legend

Winner for Energy & Big Game:

.338 ARC

Winner for Recoil & Cost:

.400 Legend

Winner for AR-15 Versatility:

Tie
Both run beautifully on the AR-15 with correct barrels and magazines.

.338 ARC vs .400 Legend — Ballistics, Use Cases & Optimal Barrel Lengths

.338 ARC is the clear winner for long-range, high-energy hunting from an AR-15—offering exceptional ballistics that surpass many legacy rifle cartridges.

.400 Legend is the winner for Midwest hunters needing a legal, accurate, low-recoil straight-wall cartridge that performs beautifully inside traditional deer-hunting distances.

Both are outstanding choices, and the real winner depends entirely on your terrain, state laws, and hunting style.