Description
Performance Overview
Velocity: 1050 FPS
Kinetic Energy: 735 ft-lbs
"Slow Jam"
The "Slow Jam" is the ultimate subsonic .338 ARC round, carefully crafted for precision and performance. Featuring a solid copper 300-grain rapid-expanding projectile, this round delivers devastating terminal performance while maintaining exceptional accuracy. Traveling at subsonic speeds, "Slow Jam" is designed for suppressed shooting, offering a quiet, efficient, and highly effective solution for hunting, training, or tactical use. In this load we are utilizing a Maker solid copper expanding projectile that delivers the terminal profile we know and love in the form of triple diameter expansion.
The .338 ARC exists because people kept pushing small-frame gas guns into territory they were never supposed to reach—and it turns out they do it extremely well. This round is exceptionally accurate in 1:5 twist barrels.
Designed as a true subsonic-first cartridge, .338 ARC delivers heavy-for-caliber projectiles with impressive efficiency from short barrels while remaining AR-15 compatible. It provides a meaningful step up from .300 Blackout without moving to a large-frame platform, making it well suited for suppressed use, hunting, and specialized precision applications where mass, consistency, and terminal performance matter more than velocity.
This 300 gr Solid Copper Expander was engineered specifically around the strengths and constraints of the .338 ARC.
Machined from solid copper, the projectile offers controlled, reliable expansion at subsonic velocities while maintaining structural integrity and deep, straight-line penetration. Monolithic construction eliminates jacket separation and ensures consistent performance across a wide range of impact conditions.
Stability and rotational limits were a core part of the design. This projectile is optimized for 1:5 twist barrels, where it demonstrates excellent gyroscopic stability and accuracy. It is safe to use in slower twist rates such as 1:6 or 1:7, though peak performance is achieved at 1:5. Twist rates faster than 1:5 are not compatible, as excessive rotational stress may compromise projectile integrity.
This round remains the pinnacle of subsonic 338 arc terminal performance.
2 Reviews Hide Reviews Show Reviews
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338ARC “Slow Jam” 300gr Sub
I have taken an 8pt and 10pt buck so far this year with the 338 ARC “Slow Jam” 300gr subs. Out of an 8.5” 1:8 KAK barrel. I was about 60-80y on both shots. Both deer only went about 10y after being hit. The first deer the round passed all the way through, the second round was recovered in the 10pt. Only one of the peddles on the round that was recovered in the deer had opened, but did catastrophic damage to the heart. Both rounds were extremely accurate and very quiet. I would highly recommend this loading over the Hornady 307gr subs.
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Phenomenal expansion and hard hitting.
Best .338 arc rounds I’ve used, very accurate. very reliable. Def worth it. Shot out of 8inch barrel with a 1-5 twist rate.
