The 300 HAM'R is a centerfire rifle cartridge developed for the AR-15 platform, designed to deliver more energy than the 5.56 and 300 Blackout supersonic loads while using standard AR-15 magazines. It is oriented toward hunting and recreational use.

The 300 HAM'R was developed to push the hunting capability of the AR-15 platform, engineered to deliver more energy than the 5.56 NATO and more than supersonic 300 Blackout loads, while still functioning with standard AR-15 magazines and bolt. Its design intent was a more effective AR-15 hunting cartridge for deer-class game at practical ranges. Ballistically the 300 HAM'R fires a .30-caliber bullet at moderate velocity, delivering solid energy for deer-class hunting and recreational use at short-to-moderate range from the compact AR-15 platform. It positions itself between the 300 Blackout and larger AR cartridges in terms of supersonic energy, aimed specifically at hunters who want effective .30-caliber performance from a standard AR-15. As a more specialized cartridge associated primarily with a particular design lineage, its rifle and ammunition availability is narrower than mainstream rounds, centered on the platform and components built around it. It occupies a hunting-focused niche within the broader family of AR-15 cartridges. Today the 300 HAM'R is used for moderate-range hunting, recreational shooting, and target shooting in the AR-15 platform, with availability centered on its supporting components and ammunition. Its pairing of improved .30-caliber hunting energy with standard AR-15 compatibility is what defines its niche.

General information about this caliber — not a recommendation for this specific firearm.