Maine-based Hydra Weaponry has beefed up their pistol-caliber carbine game with a new 10mm option. At SHOT Show, they’re displaying their new Marck-15 Hydra 10mm H21, a new configuration of their Hydra semi-auto design.

Hydra’s claim to fame has long been their switch-your-caliber AR-pattern designs, allowing them to run a wide range of calibers from a rifle with only a few basic parts changed out. In this case, the Marck-15 Hydra 10mm H21 is configured to use Glock-pattern magazines (chambered in 10mm, of course). The rifle comes with the Hydra Modular lower receiver, the 10mm H21 magazine well, the Hydra Quick Change Barrel Upper Receiver (QCB-D), a 16-inch Hydra 10mm Blowback Barrel, a 10mm Blowback Bolt, and a stock and pistol grip from B5 Systems.

Rails along the top and sides of the barrel shroud make it easy to attach optics and other accessories, and a rail underneath the barrel is ideal for a light or a foregrip. This rifle ships with a single Glock-pattern mag as well. Buyers can opt for M-Lok, Picatinny or Keymod inserts on the rifle.

But all this is just a starting point. Hydra says: “With this base rifle, you can purchase and utilize the rest of an ever-growing system including our various magazine wells and caliber conversions. To convert this system to another caliber, the most you will need to change is the barrel, bolt and bolt carrier, and magazine well to the desired caliber.” So this PCC is like their other Hydra-system rifles, and easily converted to 9mm or other chamberings.