The Daniel Defense DDM4 300S upper receiver group brings serious performance to a compact platform. Built around 300 Blackout, this 10.3" short-barrel upper delivers .30 caliber energy in a fast-handling package that works with standard 5.56mm magazines and bolts—no platform conversion needed. Whether you're building a suppressed home-defense rifle, a nimble hunting upper, or a tactical SBR, the 300S gives you the ballistics and handling that make sense in tight spaces without sacrificing reliability or durability.
The 10.3" barrel is hammer-forged chrome moly in a Strength-to-Weight profile with a 1-in-8 twist, optimized for 300 Blackout performance. The muzzle is threaded 5/8 x 24 TPI and ships with a pinned, low-profile gas block machined from hardened 4140 steel. That steel gas block doesn't add unnecessary weight, and the pinned design keeps zero rock-solid through extended strings of fire. The included extended flash suppressor is 17-4 PH stainless steel, purpose-built for this platform.
Daniel Defense's quality standards show in the details: hard coat anodized finish for durability, chrome-lined M16 profile bolt carrier group for reliability, and a genuine 9" DDM4 rail that's rugged and modular. This upper handles suppressed rounds smoothly, runs clean, and accepts standard AR handguard accessories. It's the upper half of a serious, compact rifle.
| Caliber | 300 Blackout (300 BLK) |
| Barrel Length | 10.3" |
| Barrel Material | Hammer-forged chrome moly |
| Barrel Profile | Strength-to-Weight (S2W) |
| Twist Rate | 1:8 |
| Muzzle Thread | 5/8 x 24 TPI |
| Gas Block | Pinned, low-profile, 4140 hardened steel |
| Gas System | Pistol length |
| Bolt Carrier Group | Chrome-lined M16 profile |
| Rail | 9" DDM4, 6061-T6 aluminum |
| Flash Suppressor | Extended, pinned, 17-4 PH stainless steel |
| Finish | Hard coat anodized |
| Magazine Compatibility | Standard 5.56mm AR magazines |
Yes. The 300S is designed to run standard 5.56mm AR magazines and bolts, so no proprietary parts or magazine conversions are necessary.
Yes. The 300 Blackout cartridge was developed for suppressed operation, and the 10.3" barrel with threaded muzzle makes this upper an excellent choice for suppressed hunting, home defense, and tactical shooting.
The upper includes the barrel, bolt carrier group, gas block, extended flash suppressor (pinned), Daniel Defense 9" rail, and charging handle attachment points. You'll need a lower receiver to complete the rifle.
300 Blackout is designed for short-barrel rifles and suppressed shooting. It delivers .30 caliber performance with greater muzzle energy than 5.56mm, making it effective for home defense, hunting, and tactical applications where a compact, quiet platform is an advantage.
Daniel Defense
Daniel Defense
Daniel Defense
Daniel Defense
