300 AAC – 220 gr OTFB – Remington (21422 – L300AAC4) – 200 Rounds

Running a 300 Blackout behind a suppressor is a big part of the cartridge’s appeal, and subsonic ammo is what makes it quiet. This listing is Remington UMC 300 AAC Blackout 220 grain open tip flat base ammo, MPN L300AAC4 (Remington item 21422), sold as a 200 round case packed in 20 round boxes for easy loading and storage. It is a sensible way to learn how your suppressed setup behaves before choosing a hunting load.

Remington rates L300AAC4 at 940 fps with 432 ft-lbs of muzzle energy. Staying under the roughly 1,100 fps speed of sound removes the sonic crack, so a suppressed rifle is noticeably quieter. The heavy 220 grain bullet preserves useful energy at low velocity. UMC is Remington’s value line, and this open tip flat base bullet is a target projectile, so the load is a practical choice for suppressed practice and plinking rather than hunting.

It fits rifles and pistols chambered in 300 AAC Blackout, including AR-15 uppers in 300 BLK, SIG MCX Spear LT and Rattler, Q Honey Badger, Ruger American Ranch, and Thompson Center or CVA single shots. A common question is whether a 300 Blackout upper needs special parts to run subsonic. The bolt, buffer, and magazines are standard AR parts, but short gas systems and suppressors help subsonic loads cycle, and some rifles need an adjustable gas block. Another common question is how far subsonic 300 BLK is useful. Its curved trajectory makes it most practical inside about 100 yards.

Remington L300AAC4 is new production ammunition, not reloads, made in the USA. It uses reloadable brass cases with boxer primers and is non-corrosive. This listing ships as 10 boxes of 20 rounds, 200 total, all from one lot. Twenty round boxes are handy for filling a single magazine and keeping subsonic ammo clearly separated from supersonic loads and from 223. Keep it stored dry and labeled so it never ends up in a 223 magazine.