One Horse OH-15 6mm ARC 18" 30rd Rifle

6mm ARC was drawn up to give the AR-15 more reach than 5.56 without moving to a larger receiver, and this One Horse build leans into that. The 18 inch HBAR profile barrel is heavier than a carbine barrel, which slows heat soak on longer strings and steadies the gun on a bag or a bipod. A mid length gas system spreads the pressure curve out and takes some of the harshness out of the cycle. The muzzle is threaded 5/8-24 and wears an A2 device that a brake or a suppressor mount can replace.

The rest of it is standard AR-15 hardware, which is the point. A 15 inch M-LOK handguard leaves room for hand stops and bipods anywhere along its length, a mil spec buffer tube sits under a six position M4 stock, and the grip and charging handle are common patterns. Nothing proprietary to hunt down later. One 30 round 6mm ARC magazine comes with the rifle. Loaded with heavy match bullets the cartridge stays supersonic well past where 5.56 gives up, and recoil stays mild enough to spot your own hits through the optic. Steel at distance, hogs, and deer where the caliber is legal.