Huldra rifles are manufactured exclusively by Adams Arms, and they all utilize Adams Arms’ proprietary gas piston system. Adams Arms was one of the earliest producers of piston-operated guns, and it was the first manufacturer to offer a patented retrofit system to convert direct impingement guns to its gas piston system.

This Mark IV is Chambered for 5.56mm NATO, and will also handle any of the lower-pressure .223 rounds available on the market. The 16-inch barrel has a 1-in-7-inch twist rate, which optimizes it for use with 62-grain or heavier loads. M4 feed ramps are used, and the barrel is of the government profile. It is made from CrMoV 4150 steel and is capped with a standard A2 flash suppressor. Both the piston system parts and the barrel have been treated with a proprietary salt-bath-nitride Meloniting process, which, according to Huldra, provides protection that is harder than chrome.