The AR-180 weighs in slightly over 6 pounds and measures 38 inches long. The AR-180’s 18-inch barrel features a 1-in-12-inch twist rate, as found on the original M16. The AR-180 has a true 5.56mm chamber, enabling it to fire both 5.56mm and .223 Remington loads. The AR-180 takes a magazine very similar to the AR-15, though with the magazine catch slot located on the right side. This is a different spot than typical AR-15 magazines with a magazine catch on the left side. Original AR-18/180 magazines are costly, but fortunately alteration of AR-15 magazines is a relatively simple affair, ensuring a supply of magazines.The AR-18/180 was the latest iteration of the then-new method of rifle construction featuring stamped and welded steel fabrication. It is. for all intents and purposes. a scaled-down version of the 7.62 NATO-caliber ArmaLite AR-16. As mentioned, the AR-18/180 utilizes a short-stroke piston to facilitate operation. The rifle retains the familiar rotating bolt of the AR-15/M16, mounted in a carrier, but the carrier rides on a pair of guide rods. Instead of a buffer-spring unit contained in the buttstock as the AR-15/M16 has, the AR-18/180 utilizes a pair of action springs on the guide rods.