338 ARC Load Data – 338 ARC Reloading Data

Finding precise 338 ARC load data is essential for maximizing the subsonic and supersonic capabilities of Hornady’s revolutionary heavy-hitting AR-15 cartridge.

This guide compiles verified 338 ARC reloading data to help you safely develop the perfect suppressed hunting round or high-energy supersonic load.

Whether you are loading lightweight 175-grain match bullets or heavy 307-grain Sub-X projectiles, always cross-reference these published figures before charging your cases.

338 ARC Load Data

Bullet	Bullet Weight	Powder	Published Starting Load	Published Maximum Load	Published Velocity	Barrel Length / Firearm	Source
Hornady HP Match	175 gr	CFE BLK	18.0 gr	21.0 gr	1,800 – 2,100 fps	16″ / CMMG Mk4	Hornady
Hornady InterLock SP-RP	225 gr	WIN 296	14.5 gr	15.7 gr	1,400 – 1,500 fps	16″ / CMMG Mk4	Hornady
Hornady InterLock SP-RP	225 gr	Power Pro 300-MP	14.7 gr	16.4 gr	1,400 – 1,550 fps	16″ / CMMG Mk4	Hornady
Hornady InterLock SP-RP	250 gr	WIN 296	12.3 gr	13.4 gr	1,100 – 1,200 fps	16″ / CMMG Mk4	Hornady
Hornady InterLock SP-RP	250 gr	Power Pro 300-MP	11.6 gr	14.2 gr	1,100 – 1,300 fps	16″ / CMMG Mk4	Hornady

338 ARC Reloading Data

Bullet	Bullet Weight	Powder	Published Starting Load	Published Maximum Load	Published Velocity	Barrel Length / Firearm	Source
Hornady FMJ	285 gr	Power Pro 300-MP	10.8 gr	11.7 gr	1,000 – 1,050 fps	16″ / CMMG Mk4	Hornady
Hornady FMJ	285 gr	Accurate 1680	11.2 gr	12.5 gr	950 – 1,050 fps	16″ / CMMG Mk4	Hornady
Hornady A-Tip Match	300 gr	CFE BLK	11.5 gr	12.8 gr	950 – 1,000 fps	16″ / CMMG Mk4	Hornady
Hornady Sub-X	307 gr	Accurate 1680	11.0 gr	12.0 gr (52,000 PSI)	950 – 1,050 fps	16″ / CMMG Mk4	Hornady
Hornady Sub-X	307 gr	WIN 296	10.0 gr	11.2 gr	950 – 1,050 fps	16″ / CMMG Mk4	Hornady

Understanding the 338 ARC Reloading Data

The 338 ARC (Advanced Rifle Cartridge) was designed by Hornady to deliver massive terminal energy from the standard AR-15 platform by necking up the 6.5 Grendel parent case to accept .338-caliber bullets. Reading the tables above requires understanding that the cartridge serves two entirely different purposes: supersonic precision and heavy subsonic suppression. Because of the massive variations in bullet length, reloaders must strictly adhere to the 2.260-inch maximum overall length (OAL) so the fat, heavy rounds feed reliably from dedicated 338 ARC magazines without pinching in the chamber.

338 ARC Bullet Weight Reloading Data

The bullet weight spectrum for the 338 ARC is exceptionally broad, generally ranging from 170 grains up to a massive 307 grains. Supersonic loads typically utilize 170-grain to 225-grain bullets, offering excellent short-to-medium range terminal performance. The cartridge’s true identity, however, is built around heavy subsonic performance using 285-grain, 300-grain, and 307-grain projectiles. A fast 1:8 barrel twist rate is standardized across the platform to ensure these extremely long, high-mass bullets fully stabilize at low speeds.

338 ARC Powder Reloading Data

Powder selection for the 338 ARC revolves entirely around magnum pistol powders and the absolute fastest-burning rifle propellants, much like the popular 300 Blackout but scaled for a larger case. Powders such as Accurate 1680 and Hodgdon CFE BLK are universally recommended because they provide enough gas volume to reliably cycle an AR-15’s gas system. Other exceptional propellants include Winchester 296 (W296), Lil’Gun, and Power Pro 300-MP, which provide excellent case fill density for both supersonic and subsonic loads.

338 ARC Bullet and Powder Combinations

Pairing the right bullet with the appropriate powder ensures the rifle cycles flawlessly while maintaining the desired velocity bracket. When loading heavy 307-grain subsonic hunting bullets, utilizing Accurate 1680 or CFE BLK is the most reliable way to generate the required port pressure to operate the AR-15 bolt without accidentally breaking the sound barrier. For supersonic applications using 175-grain to 225-grain bullets, powders like W296 and Power Pro 300-MP offer highly efficient burns that maximize muzzle velocity out of short tactical barrels.

338 ARC Velocity From Published Data

Published velocity figures for the 338 ARC highlight its unique, dual-purpose ballistic profile. Supersonic loads utilizing lighter 175-grain bullets can comfortably achieve 1,900 to 2,100 fps, producing a practical hunting trajectory out to 250 yards. Subsonic load data is deliberately calibrated to keep heavy 285-grain to 307-grain bullets hovering strictly between 950 and 1,050 fps, guaranteeing the projectile remains quietly below the speed of sound regardless of altitude or temperature shifts.

338 ARC Reloading Data by Barrel Length

Manufacturer testing for the 338 ARC is predominantly conducted using a 16-inch laboratory barrel. Because the cartridge utilizes very fast-burning powders, it achieves complete combustion quickly, making it incredibly efficient in short-barreled rifles (SBRs) featuring 8.5-inch to 12.5-inch barrels. If you fire a standard 16-inch load from an 8.5-inch barrel, expect a modest velocity loss. You must carefully chronograph your subsonic handloads in your specific barrel length to ensure they do not drop too slow and cause cycling failures.

338 ARC Energy and Ballistics

The most significant advantage of the 338 ARC is its massive kinetic energy retention at subsonic speeds. While a standard subsonic 300 Blackout generates roughly 480 foot-pounds of energy, the 338 ARC firing a 307-grain bullet produces an astonishing 752 foot-pounds of energy at the muzzle—roughly 1.5 times the power. Because it features a massive .338-inch frontal diameter, it transfers this energy immediately upon impact, though its heavy, slow flight path produces a steeply arched trajectory past 150 yards.

338 ARC Hunting Applications

The 338 ARC was engineered from the ground up as a premier short-range, suppressed hunting cartridge. It is devastatingly effective on feral hogs, whitetail deer, and black bear inside 200 yards. The 307-grain Hornady Sub-X bullet expands reliably even at velocities as low as 900 fps, creating massive wound channels that traditional subsonic rounds struggle to match. The supersonic loads provide hunters with a bit more reach for open pasture shots without requiring an entirely new rifle platform.

Manufacturer Data vs. Independent Testing

Because the 338 ARC operates in the specialized world of heavy subsonics and utilizes the 6.5 Grendel bolt face, adhering to official manufacturer data is absolutely paramount. Independent forum data may feature wildcat equivalents (like the older .338 Spectre), but these do not perfectly map to the SAAMI-approved ARC chamber dimensions. Always use official manufacturer data to avoid squib loads that can lodge a heavy bullet in your bore or overpressure loads that can shear the AR-15’s bolt lugs.

338 ARC Pressure and Safety

The SAAMI Maximum Average Pressure (MAP) for the 338 ARC is firmly set at 52,000 PSI to safely operate within the structural limits of an AR-15 bolt carrier group. When reloading subsonic ammunition, the primary safety hazard is actually low pressure, which can cause a failure to cycle or lead to a dangerous squib load. Always visually inspect the powder level in every case to ensure you have not thrown a double charge, as the small fast-burning powder charges can easily fit twice inside the case.

Best Sources for 338 ARC Reloading Data

The most reliable source for load data is Hornady, the company that developed and standardized the cartridge. Hornady provides meticulously tested, platform-safe load data in their official reloading app and published PDF supplements tailored specifically to their bullets. Additionally, powder manufacturers like Hodgdon routinely update their Reloading Data Center with tested recipes for CFE BLK and Accurate 1680, guaranteeing you have access to safe, pressure-tested baselines.

Frequently Asked Questions

Where can I find 338 ARC reloading data?

You can find official, pressure-tested 338 ARC reloading data directly through the Hornady Reloading App, their published supplemental PDFs, and digitally on the Hodgdon Reloading Data Center.

What powders are listed in published 338 ARC data?

Commonly listed powders include fast-burning rifle and magnum pistol propellants such as Accurate 1680, Hodgdon CFE BLK, Winchester 296, Lil’Gun, and Power Pro 300-MP.

What bullet weights are covered in these tables?

These tables cover dual-purpose bullet weights, spanning from 175-grain supersonic projectiles up to massive 307-grain heavy subsonic bullets.

Does barrel length affect 338 ARC velocity?

Yes, shooting from an 8.5-inch or 10.5-inch barrel rather than the standard 16-inch test barrel will lower velocities, requiring you to carefully chronograph your loads to ensure proper subsonic tuning.

Can I use standard rifle primers for 338 ARC?

Yes, standard small rifle primers (such as the Federal 205) are universally specified in manufacturer load data to safely ignite the powder column inside the small primer pocket brass.

What is the difference between 338 ARC load data and reloading data?

There is no practical difference; both terms refer to the exact recipes of powder charges, bullet weights, and primers required to safely assemble the cartridge.

Why do published velocity figures differ between sources?

Velocity figures differ because testing facilities utilize different test barrel lengths, distinct environmental conditions, variations in brass case volumes, and different primer types during their protocols.

Should I use the maximum published load?

For supersonic loads, never start at the maximum; always begin at the starting charge and work up. For subsonic loads, you typically start near the maximum subsonic charge and cautiously work your powder charge down until your rounds reliably stay below the speed of sound.

Can I use data from one bullet manufacturer for another bullet?

You should only use data specifically designed for the exact bullet you are loading, as variations in bullet length, profile, and bearing surface dramatically alter internal case capacity and chamber pressures.

Where should I verify 338 ARC load data before reloading?

You should strictly verify all load data against an official, recently published manufacturer manual or a powder company’s official online database before assembling any ammunition.