The A4 stripped upper is ubiquitous with the modern AR-15. A2 rear sight with windage & elevation adjustments.New shell casing deflector behind dust cover.All other components - including the A2-style upper - remained the same. The trigger assembly was modified in the A3 to provide full-auto fire. Although the carry handle and general profile remained the same as the A1 rifle, the A2 upper once again changed the rear sight aperture with a more robust and distance-adjustable assembly. The horizontal finger wheel returned for windage adjustments, and the aperture could be raised or lowered with a side-mounted elevation knob to accommodate specific shooting distances, up to 800 yards.Ī shell casing deflector was added just behind the ejection port to reduce interference and injury to the shooter from spent brass. The M16A3 is a modified version of the M16A2, produced in small numbers and primarily issued to members of the SEALs, Seabees, and security units. With it came an updated stripped upper receiver. The M16A2 represented an improvement over the A1's finicky Vietnam-era design. The A2 upper was also the first receiver to be used on the M4 carbine, dubbed the XM4 in development, introduced in 1984. While the A1 upper doesn't have a modern rail system, it still allows for the installation of optics and scopes: A center-drilled hole inside the carry handle acts as a singular mounting point for a basic scope mount or a modern Picatinny rail. This attachment system is popular among builders who want to replicate theĬAR-15 XM177, a short-barreled variant of the A1 rifle (introduced in 1966 for American Special Forces) dubbed the "Commando". The rear sight included two apertures: Features The windage knob for the rear sight was also redesigned to rest flush against the carry handle, rather than protrude as a horizontal finger wheel. The forward assist was also added to ensure the bolt could be forced into battery should the receiver get dirty or "gunked up" in the field. When the U.S Army asked ArmaLite to develop the AR-15, the design was updated, moving the the charging handle to the rear of the receiver. The very first upper had the charging handle inside the carry handle. The original AR-type upper did not have a forward assist nor a cut-out for the modern, rear-facing charging handle. This classic profile is most often recognized by its integrated rear sight aperture and carry handle. A1 UPPER RECEIVERĮugene Stoner's original ArmaLite AR-10 Rifle, introduced in 1956, was fitted with an early version of the M16A1-type upper receiver. Let's take a look at the stripped uppers from oldest to newest, and note each feature present (or lacking). This guide covers the various types of stripped uppers available for your build, the history of past receivers not frequently seen today in the market, and the various types of features you can pick from to help complete your build.
A2 CARRY HANDLE RECEIVER INSTALL
Opportunity to customize your build truly begins with the stripped upper receiver, and the parts you install on it. The AR-15 platform's lower receiver is relatively standardized. This guide is part of our Master Guide to AR-15 Parts)