Over the past several years, I have written two evaluations on Daniel Defense’s MK18 short-barreled rifle (SBR). Its 10.3-inch barrel is chambered in 5.56mm NATO, and it’s the ideal size for close quarters while retaining a long-range capability.

With the increasing popularity of the 300 Blackout cartridge, it was only a matter of time before Daniel Defense introduced a version in a similar configuration. The new Daniel Defense DDM4 300S is that rifle.

Built around Daniel Defense’s quality cold-hammer-forged barrel, the DDM4 300S has all of the mil-spec features of the MK18, including upper and lower receivers that are machined from 7075-T6 aluminum before being Type III hardcoat anodized.

The chrome-moly-vanadium steel barrel has a 1-in-8-inch twist rate and a salt-bath nitride finish. The pistol-length gas system ensures reliability with the 300 BLK cartridge. As for the lower, you’ll find standard AR controls while both the pistol grip and buttstock are Daniel Defense’s own designs, which features Soft Touch rubber overmolded panels.

I recently had an opportunity to evaluate a DDM4 300S upper on a registered SBR lower. The system was 100-percent reliable with a wide variety of ammunition.

We also used a Gemtech GM-9 suppressor with a Multi-Mount adaptor that allowed the suppressor to thread directly to the barrel. Even though the GM-9 is a pistol suppressor, it is rated for use with 300 BLK subsonic ammunition.

Using Daniel Defense’s new 200-grain subsonic load and Gemtech 187-grain subsonic load, the rifle/suppressor combo proved very effective.

Look for a complete review of the Daniel Defense DDM4 300S in an upcoming issue of TACTICAL WEAPONS. To subscribe, visit

For more information on the Daniel Defense DDM4 300s, please visit

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