Hornady 338 ARC ($25 – $29 per box of 20)

Hornady’s new 338 ARC (Advanced Rifle Cartridge) may be the ultimate subsonic round. Based on the 6.5mm Grendel parent case, the cartridge is designed for AR-15s and micro-action bolt guns. It uses the same magazines as the Grendel/ARC family of cartridges, so you need only put a new upper on a lower to have a 338 ARC rifle. The cartridge uses a 1:8 twist rate to stabilize long, heavy bullets.

The 338 ARC produces consistent pressure and cycles reliably in both subsonic and supersonic loads used with or without suppressors. You can use the same gas settings in an AR-15 with either type of load. Initial offerings include a 307-grain Sub-X bullet in the Subsonic line and a 175-grain Hornady Black load. Advertised velocity for the 307-grain load is 1,050 fps out of a 16-inch barrel, while the 175-grain H Match Black load steps out at 2,075 fps from the same-length barrel.

The 307-grain load delivers 1.5 times more energy and improved terminal ballistics over the 300 Blackout. The 8.6 Blackout, in comparison, requires AR-10-sized rifles and isn’t fully optimized for subsonic performance. For more information, contact Hornady; Tel.: (800) 338-3220; Web: www.hornady.com.