{"product_id":"rra-cmplt-mid-a4-upr-450bm-16-5rd","title":"Rock River Arms Complete Mid-Length A4 Upper Receiver .450 Bushmaster 16\" – AR-15 Platform","description":"\u003cp\u003eThe Rock River Arms Complete Mid-Length A4 Upper Receiver delivers straight-wall cartridge performance in .450 Bushmaster for AR-15 lower receivers. This 16-inch configuration is purpose-built for hunters in straight-wall states and shooters seeking substantial stopping power at moderate range. The mid-length gas system provides reliable cycling with this hard-hitting caliber while managing recoil effectively.\u003c\/p\u003e\u003cp\u003eConstructed from forged aluminum with a durable finish, this complete upper assembly arrives ready to install on any mil-spec AR-15 lower receiver. The A4 flat-top design accepts standard optics and iron sights. Installation requires no gunsmithing—simply attach to your lower receiver using standard takedown pins. Ships with a 5-round magazine to comply with hunting regulations in many jurisdictions.\u003c\/p\u003e\u003cul\u003e\n\u003cli\u003e\n\u003cstrong\u003eCaliber:\u003c\/strong\u003e .450 Bushmaster\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003eType:\u003c\/strong\u003e Complete Upper Receiver Assembly\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003eCompatible Lower:\u003c\/strong\u003e Mil-spec AR-15\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003eBarrel Length:\u003c\/strong\u003e 16 inches\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003eGas System:\u003c\/strong\u003e Mid-length\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003eMaterial:\u003c\/strong\u003e Forged aluminum upper receiver\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003eConfiguration:\u003c\/strong\u003e A4 flat-top\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003eIncludes:\u003c\/strong\u003e 5-round magazine\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003eInstallation:\u003c\/strong\u003e Drop-in, no gunsmithing required\u003c\/li\u003e\n\u003c\/ul\u003e","brand":"Rock River Arms","offers":[{"title":"Default Title","offer_id":47939763994879,"sku":"RRA450B0592","price":750.95,"currency_code":"USD","in_stock":true}],"thumbnail_url":"\/\/cdn.shopify.com\/s\/files\/1\/0729\/0434\/3807\/files\/2950207.jpg?v=1766546470","url":"https:\/\/doublestackstore.com\/products\/rra-cmplt-mid-a4-upr-450bm-16-5rd","provider":"Double Stack Store","version":"1.0","type":"link"}