Primary Weapons Systems (PWS) manufactures piston-operated AR-15 and AR-10 pattern rifles in Boise, Idaho. The MK116 Pro uses PWS's long-stroke piston system — one of the few AR-pattern rifles using a long-stroke (rather than short-stroke) piston arrangement — with an adjustable gas block. Long-stroke piston systems are smoother and more reliable with a wider range of ammunition but add weight forward. Type: Rifle Action: Semi-Automatic Caliber: 5.56x45mm NATO Capacity: 30 Year introduced: 2009, USA Weight: 104 oz Overall length: 35.5" Status: Active Intended use: sporting, law_enforcement, tactical