{"product_id":"h-k-mr556-a4-upper-receiver-kit-5-56mm-16-5-threaded-barrel","title":"H\u0026K MR556 A4 Upper Receiver Kit 5.56mm 16.5\" Threaded Barrel","description":"\u003cp\u003eThis kit includes a complete upper receiver\/barrel assembly allowing Mil-Spec 5.56mm AR-style rifles to be retrofitted to HK’s piston and pusher rod system. This system utilizes a piston and a pusher rod in place of the gas tube normally found in AR15\/M16\/M4-style rifles. This closed system virtually eliminates the malfunctions that are common in direct-impingement gas systems since hot carbon fouling and waste gasses are not propelled into the receiver area to operate the action. This is the same key feature critical to the success of the HK416 used by elite military and law enforcement customers.\u003cbr\u003eFeatures\"\u003c\/p\u003e\u003cul\u003e\t\u003cli\u003eComplete MR556 A4 Upper Receiver\/Barrel Assembly— HK 16.5 inch cold-hammer forged barrel upper receiver with forward assist extended convertible charging handle HK Free Floating Rail System handguard\u003c\/li\u003e\t\u003cli\u003eComplete MR556 Bolt Group Assembly\u003c\/li\u003e\t\u003cli\u003eTungsten Filled HK Proprietary Buffer\u003c\/li\u003e\t\u003cli\u003eHK Proprietary Buffer (Action) Spring\u003c\/li\u003e\t\u003cli\u003eAdjustable Gas Block\u003c\/li\u003e\t\u003cli\u003eShips in HK Soft case.\u003c\/li\u003e\n\u003c\/ul\u003e\u003cbr\u003eUppers\u003cbr\u003e51000384","brand":"Heckler \u0026 Koch Inc.","offers":[{"title":"Retail","offer_id":48898292220041,"sku":"HZ51000384","price":1791.0,"currency_code":"USD","in_stock":true},{"title":"Member","offer_id":48898306080905,"sku":"HZ51000384","price":1791.0,"currency_code":"USD","in_stock":true},{"title":"Premium Member","offer_id":48898306113673,"sku":"HZ51000384","price":1791.0,"currency_code":"USD","in_stock":true}],"thumbnail_url":"\/\/cdn.shopify.com\/s\/files\/1\/0659\/2813\/4793\/files\/HZ510003842.jpg?v=1793852106","url":"https:\/\/christianvigilant.com\/products\/h-k-mr556-a4-upper-receiver-kit-5-56mm-16-5-threaded-barrel","provider":"Christian Vigilant","version":"1.0","type":"link"}