What twist rate does .338 ARC use?

.338 ARC typically uses a 1:8 twist rate.

What bullet diameter is .338 ARC?

.338 ARC uses a 0.3383″ (8.593 mm) diameter bullet.

Is .338 ARC still in production?

.338 ARC is active; typical availability is common.

What is .338 ARC used for?

.338 ARC is primarily used for military, tactical, hunting.

What is .338 ARC based on?

.338 ARC is derived from the 6mm ARC case.

Lindcott Armory

Rifle · SAAMI

.338 ARC

Also known as .338 Advanced Rifle Cartridge

Hornady's AR-15 compatible .338 caliber cartridge offering both supersonic hunting performance and 1.6x the subsonic energy of .300 Blackout..

Caliber: 0.3383″ · 8.593 mm
Introduced: 2025
Case: Rebated
Parent: 6mm ARC
Primary use: Military, Tactical, Hunting
Status: Active

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VelocityBeing verified

EnergyBeing verified

Typical grains185 · 250 · 265 gr

Identity

Introduced: 2025
Type: Rifle
Origin: United States
Inventor: Hornady
Manufacturer: Hornady
Standard: SAAMI
Status: Active
Availability: Common

Build

Case capacity: 35 gr H₂O
Twist (typical): 1:8
Primer: Small Rifle
Case type: Rebated

Pressure & range

Max pressure: 52,000 psi
Eff. range: 300 yd
Max range: 1200 yd
Recoil: 20–28 ft·lb
Subsonic: Capable

Introduced by Hornady

Ballistics

Published velocity/energy data isn't available for .338 ARC. Parent case: 6mm ARC.

Performance

Best for Withheld until verified

Dimensionscase measurements · scale drawing · size vs familiar rounds

Case dimensions — the scale drawing at the top of the page is built from these.

SAAMI · verified

Measure	mm	in	✓
Bullet ⌀	8.59	0.338	✓
Neck ⌀	9.37	0.369	✓
Shoulder ⌀	10.97	0.432	✓
Shoulder angle	30°	—	✓
Base ⌀	11.20	0.441	✓
Rim ⌀	11.20	0.441	✓
Belt ⌀	n/a
Rim thickness	1.50	0.059	✓
Neck length	7.80	0.307	≈
Case length	33.02	1.300	✓
Overall length	57.40	2.260	✓

Size vs familiar rounds

Drawn at true 1:1 — every case is accurate relative to the others. Absolute size depends on your screen's pixel density, so measuring one against a real ruler may be off. .338 ARC is highlighted below.

Factory loads

Verification

Being verified

Advertised FPS, energy, and BC are withheld until loads clear verification.

Reloading costestimate cost per round vs factory

Estimate your cost per round and how it compares to factory. Inputs are yours — nothing is stored.

Powder $/lb Charge (gr) Bullet $/ea Primer $/ea Brass reuses Brass $/ea

Cost estimate only — not load data. Charge weight is your input; follow published manuals for safe charges.

Lineage

Family TreeOpen .338 ARC in the interactive cartridge family tree

Connected reference

Loads18 factory loads for .338 ARC FirearmsFirearms in .338 ARC

History

Introduced by Hornady in 2025 as a direct competitor to the 8.6 Blackout. Designed to function in AR-15 platforms with a standard bolt face. Targets both military special operations and civilian hunting markets with one cartridge covering the spectrum from suppressed subsonic to 600-yard supersonic.

FAQs

What twist rate does .338 ARC use?: .338 ARC typically uses a 1:8 twist rate.
What bullet diameter is .338 ARC?: .338 ARC uses a 0.3383″ (8.593 mm) diameter bullet.
Is .338 ARC still in production?: .338 ARC is active; typical availability is common.
What is .338 ARC used for?: .338 ARC is primarily used for military, tactical, hunting.
What is .338 ARC based on?: .338 ARC is derived from the 6mm ARC case.

Sources & provenance

Standard SAAMI — ANSI/SAAMI Z299 — Cartridge & Chamber Drawings archived

Data & sources. Specs compiled from the Lindcott Armory reference; availability counted from 18 live factory loads; the trajectory is modeled (point-mass), not measured. See methodology. Spotted an error? Report it →