By exceeding military standards, Core Systems ensures the best fit possible and can offer a more reliable, smoother functioning, and more accurate weapon that will provide you with the peace of mind that you deserve. The Core 15 M4 Piston has a gas piston assembly with adjustable gas settings and a proprietary monolithic, melonite-coated bolt carrier that ensures unquestionable performance in any environment. The 16" M4 profile stainless steel match-grade barrel has a 1 in 8" twist and an A2 flash hider. The upper and lower receivers are constructed from Mil-Spec Forged 7075-T6 aluminum and the stock is a Core 15 six-position retractable model with an A2 pistol grip. The lower receiver has a beveled magwell for improved reloading speed, machined chevrons in the front strap, and bullet pictogram safety markings. The upper receiver has M4 feed ramps and a 1913 Picatinny flattop rail with a railed gas block up front for sight mounting. A Core 15 V.2 Hardcore Billet charging handle; M4-style Thermoset molded polymer hand guards with DualHeat Shields; and a monolithic, Melonite-coated bolt carrier ensure that your M4 Piston will operate safely and smoothly for years to come. A 30-round Magpul PMAG is included.