Reliable 338 ARC load data can be found directly through the Hornady Reloading App and the Hodgdon Reloading Data Center. Published load data for this cartridge typically includes specific powder charges, primer types, overall cartridge lengths (max 2.260″), velocities, and tested barrel lengths, which are crucial for reliable AR-15 cycling. Available data covers a unique spectrum of bullet weights, ranging from 170-grain supersonic projectiles up to massive 307-grain subsonic expanding bullets. Powder manufacturers like Hodgdon publish data utilizing fast-burning magnum pistol and blackout-style powders. It is critical to follow exact recipes because load data can vary significantly between supersonic and subsonic component combinations, altering chamber pressures and gas system timing.
338 ARC Load Data
| Bullet | Bullet Weight | Powder | Published Starting Load | Published Maximum Load | Published Velocity | Barrel Length | Source |
| Hornady MonoFlex | 170 grain | Multiple / See App | Consult Hornady App | Consult Hornady App | 2,075 fps | 16″ | Hornady Published Specs |
| Hornady HP Match | 175 grain | Multiple / See App | Consult Hornady App | Consult Hornady App | 2,075 fps | 16″ | Hornady Published Specs |
| Hornady FTX | 215 grain | Multiple / See App | Consult Hornady App | Consult Hornady App | 1,900 fps | 16″ | Hornady Published Specs |
| Frontier FMJ | 285 grain | Multiple / See App | Consult Hornady App | Consult Hornady App | 1,050 fps | 16″ | Hornady Published Specs |
| Hornady SUB-X | 307 grain | Multiple / See App | Consult Hornady App | Consult Hornady App | 1,050 fps | 16″ | Hornady Published Specs |
Understanding The 338 ARC Load Data
When evaluating published 338 ARC reload data, several data points work together to ensure your AR-15 or micro-bolt action functions safely.
- Starting load: The minimum powder charge recommended by the publisher. This provides a safe baseline to begin testing, ensuring the bullet exits the barrel without risking dangerous pressure spikes.
- Maximum published load:The absolute highest powder charge tested before encountering pressure signs or reaching the SAAMI maximum average pressure of 52,000 PSI.
- Velocity: The speed of the bullet as it leaves the muzzle, measured in feet per second (fps). For the 338 ARC, maintaining sub-1,100 fps is critical for subsonic loads.
- Pressure:The 338 ARC is unique, operating at roughly 30,000 PSI for subsonic loads and up to 52,000 PSI for supersonic variants.
- Bullet weight: The mass of the projectile in grains.
- Powder: The specific chemical propellant used. Burn rates are highly specific; 338 ARC utilizes fast-burning powders that cannot be interchanged.
- Barrel length: The length of the test barrel dictates the velocity. Hornady’s published benchmark velocities utilize a 16-inch barrel.
- Test conditions: Altitude, temperature, and atmospheric pressure affect ballistics and the speed of sound, which is highly relevant for subsonic 338 ARC shooters.
Published values differ between manufacturers because every company uses slightly different test parameters, brass internal capacities, and exact bore dimensions.
338 ARC Bullet Weight Load Data
The 338 ARC was purposefully designed for heavy-for-caliber subsonic performance and moderate-range supersonic hunting.
- 170 grain: Supported by the Hornady MonoFlex. This lightweight, lead-free bullet is designed for supersonic hunting in jurisdictions requiring non-toxic ammunition.
- 175 grain:The primary supersonic target and general-purpose weight, utilized by the Hornady HP Match BLACK line, pushing past 2,000 fps.
- 215 grain:The Hornady FTX offers a heavy supersonic option for medium game, bridging the gap between velocity and mass.
- 285 grain:Featured in Frontier FMJ loads, this weight acts as a dense, cost-effective subsonic training projectile.
- 307 grain: The flagship bullet weight for the cartridge. The 307-grain SUB-X is designed specifically to expand at subsonic velocities (as low as 900 fps), providing massive terminal energy without breaking the sound barrier.
338 ARC Powder Load Data
Selecting the correct 338 ARC powder is vital. Unlike its 6mm ARC and 22 ARC siblings, the 338 ARC requires much faster-burning powders akin to the 300 Blackout.
| Powder | Bullet | Bullet Weight | Published Starting Load | Published Maximum Load | Published Velocity | Source |
| Hodgdon CFE BLK | Various | 170 – 307 grain | See Hodgdon Data | See Hodgdon Data | Varies by weight | Hodgdon / Independent |
| Accurate 1680 | Various | 170 – 307 grain | See Hodgdon Data | See Hodgdon Data | Varies by weight | Hodgdon / Independent |
| Hodgdon Lil’Gun | Various | 170 – 307 grain | See Hodgdon Data | See Hodgdon Data | Varies by weight | Hodgdon / Independent |
| Hodgdon H110 | Various | 170 – 307 grain | See Hodgdon Data | See Hodgdon Data | Varies by weight | Hodgdon / Independent |
Do not assume that a 338 ARC powder charge published for a 175-grain bullet can automatically be applied to a 307-grain bullet. Heavy subsonic bullets seat much deeper into the case, drastically reducing case capacity and altering pressure dynamics.
338 ARC Bullet And Powder Combinations
The exact combination of components in your 338 ARC load recipe dictates both safety and gas system reliability.
- Bullet construction and bearing surface:Monolithic copper bullets (like the 170gr MonoFlex) create more friction than traditional lead-core bullets, often requiring a reduction in your 338 ARC powder charge.
- Seating depth and Magazine constraints:Because the 338 ARC must fit within the AR-15’s 2.260″ magazine length restriction, heavy 307-grain bullets take up significant powder capacity.
- Case capacity:Based on the 6.5 Grendel parent case, internal volume is limited, meaning small changes in powder charge result in large pressure swings.
- Primer: Magnum primers are often utilized in independent testing with ball powders like CFE BLK and Accurate 1680 to reduce velocity standard deviations.
- Barrel characteristics:Fast twist rates (like 1:8 or faster) are required to stabilize massive 307-grain projectiles at slow subsonic speeds.
338 ARC Velocity From Published Data
Velocities for the 338 ARC vary heavily based on whether the load is designed for supersonic reach or suppressed subsonic quiet.
- 170gr MonoFlex:2,075 fps (Hornady Published Data, 16″ barrel)
- 175gr HP Match:2,075 fps (Hornady Published Data, 16″ barrel)
- 215gr FTX:1,900 fps (Hornady Published Data, 16″ barrel)
- 285gr Frontier FMJ:1,050 fps (Hornady Published Data, 16″ barrel)
- 307gr SUB-X:1,050 fps (Hornady Published Data, 16″ barrel)
It is crucial to distinguish between manufacturer-published velocities and independent chronograph testing. Calculated velocity is an estimate, whereas published data represents measured reality in a laboratory setting.
338 ARC Load Data By Barrel Length
Barrel length directly impacts the 338 ARC velocity, especially for supersonic loads. Hornady’s published benchmark velocities utilize a 16-inch test barrel. Independent testing shows that when barrel length is reduced to AR pistol lengths (e.g., 8.5″ or 11.3″), supersonic loads lose velocity rapidly, while subsonic loads are often easier to tune, as they only need to reach ~1,000 fps regardless of barrel length. Do not present one barrel’s velocity as universal; a load that is subsonic in an 8-inch barrel may go supersonic in a 16-inch barrel.
338 ARC Energy And Ballistics
The 338 ARC was engineered to outperform the 300 Blackout, specifically in subsonic energy.
- Subsonic Energy:Firing the 307-grain SUB-X at 1,050 fps yields roughly 752 ft-lbs of muzzle energy. This is approximately 1.5 times the energy of a standard 220-grain 300 Blackout subsonic load.
- Supersonic Energy:Firing the 175-grain HP Match at 2,075 fps yields about 1,115 ft-lbs of energy at 200 yards, making it a highly capable short-to-medium range brush cartridge.
The effective range for the subsonic 338 ARC is roughly 100 to 200 yards, while supersonic loads stretch practical hunting limits to approximately 200 to 300 yards depending on the target.
Manufacturer Data vs Independent Testing
When seeking a 338 ARC load recipe, reloader safety relies on understanding the source of the data.
- Manufacturer-published load data: Derived in a laboratory using SAAMI-spec pressure testing equipment. Hornady and Hodgdon provide the safest, most authoritative data.
- Independent chronograph testing: Real-world results from publications like Ultimate Reloader provide great context on how powders like Accurate 1680 and CFE BLK cycle in AR-15 gas systems.
- User-submitted load reports: Found on forums. These are anecdotal and should never be used as a primary source for powder charges.
338 ARC Pressure And Safety
Safety is paramount in 338 ARC load development. Because the cartridge uses a 6.5 Grendel bolt face (which removes material from the AR-15 bolt lugs), SAAMI accepted the cartridge with a Maximum Average Pressure (MAP) of 52,000 PSI for supersonic loads.Subsonic loads intentionally operate at roughly 30,000 PSI to ensure reliable cycling without overwhelming suppressors.
Never substitute components in published 338 ARC reloading data. Changing from one brand of brass to another alters internal capacity. Never attempt to extrapolate 338 ARC data from wildcat cartridges like the 338 Spectre. Always start at the published starting load and watch carefully for pressure signs.
Best Sources For 338 ARC Load Data
The strongest current sources for 338 ARC load data include:
- Hornady:As the inventor of the cartridge, Hornady provides the most comprehensive lab-tested load data via their reloading app and manuals.
- Hodgdon: The official Reloading Data Center is consistently updated with pressure-tested limits for powders like CFE BLK, Lil’Gun, and Accurate 1680.
- SAAMI: Provides the official dimensional drawings and pressure limits (52,000 PSI) for the cartridge.
Common 338 ARC Load Data Questions
Where can I find 338 ARC load data?
Reliable data is available in the Hornady reloading app, Hornady’s latest reloading manual, and the Hodgdon online Reloading Data Center.
What powders are used in published 338 ARC data?
Fast-burning powders commonly used for the 300 Blackout are utilized, including Accurate 1680, CFE BLK, Lil’Gun, and H110.
What bullet weights have 338 ARC load data?
Published data covers 170-grain, 175-grain, 215-grain, 285-grain, and 307-grain projectiles.
What is the best source for 338 ARC reloading data?
Hornady is the absolute primary authoritative source, as they developed the cartridge for SAAMI acceptance in 2025.
Why does 338 ARC load data vary between sources?
Data varies because different test labs use different brass (which changes internal capacity), different primers, and unique barrel lengths.
Does barrel length affect 338 ARC velocity?
Yes. Published data generally uses a 16-inch test barrel. Shorter AR-15 pistol barrels will yield lower velocities, which requires powder charge adjustments to remain subsonic.
Can the same powder charge be used with a different bullet?
No. Differences in bullet bearing surface and extreme variations in seating depth between a 175-grain and 307-grain bullet mean powder charges must be heavily tailored.
What is the difference between starting and maximum published load data?
The starting load is the safest tested minimum, while the maximum is the highest powder charge tested before reaching unsafe pressures (52,000 PSI).
Where can I find pressure-tested 338 ARC data?
Directly from manufacturer manuals and apps, including Hornady and Hodgdon.
Does Hornady publish 338 ARC load data?
Yes. Hornady championed the cartridge and provides official load data for their SUB-X, MonoFlex, FTX, and HP Match bullet lines.
Does Hodgdon publish 338 ARC load data?
Yes. Hodgdon includes the 338 ARC in their Reloading Data Center for use with their family of fast-burning powders.
Final Verdict
Reloaders looking for a 338 ARC load data chart should source their starting points directly from established manufacturers like Hornady and Hodgdon. When comparing recipes, always pay close attention to the specific bullet weight and barrel length, as the cartridge acts very differently when loaded with a 175-grain supersonic projectile versus a massive 307-grain subsonic bullet. Because the 338 ARC relies on AR-15 magazine restrictions and a 6.5 Grendel bolt face, adhering to precise, component-specific published load data is the only way to guarantee both semi-automatic reliability and absolute safety during load development.