The Armalite X03 Prototype AR-10A Select Fire

By: Hayden Foster, IMT Assistant Curator

Following the X01 and X02 the X03, also called the AR-10A, was demonstrated at several military installations across the United States. X03 incorporated several features that make it unique compared to later AR models. Some of the unique features found on X03 include the upper and lower receiver mating, the one piece bolt carrier and buffer, and hybrid flash hiding compensator.

                Unlike the latter AR-10 and AR-15 designs common today, X03 AR-10A is noticeably different in regards to its receiver design. There are a few features that can still be found, like the incorporation of the rear sight into a monolithic “carry handle” on top of the receiver, the allocation of control groups and parts between the upper and lower receiver groups, and the use of 7075 aerospace aluminum in the construction of the receivers. The similarities largely end there, with one of the most noticeable differences being the way the upper and lower receivers interconnect. Instead of utilizing two takedown pins to hold the upper and lower receiver together like later versions, X03 uses flanged upper receiver tracks that slide onto grooves on the lower receiver. Once the upper receiver is in position on the lower, a single takedown lever rotates to secure the two together.

                Another feature unique to X03 that is not found on later AR-10s is the single piece bolt carrier and buffer. On the AR-10 and AR-15 designs found today, the buffer and bolt carrier group are found as two separate items split between the upper and lower receiver groups. On X03, the bolt carrier group and buffer are all one piece with a detachable side mounted charging handle. During takedown on the X03 the buffer and carrier combo stay attached to the lower receiver group.  The charging handle design is worth mention as well in that it protrudes off the right side of the carrier, reciprocates with the bolt, and must be detached from the carrier in order for the upper receiver to slide free of the lower receiver. This differs from the charging handle design found on AR-10 designs immediately after X03 that were relocated vertically into the carry handle.

                The last novel feature of the X03 is its hybrid flash hiding muzzle device. Unlike the common flash hiders encountered today that utilize large open slits to break up the muzzle blast, X03’s muzzle device incorporates a large cylinder with smaller holed drilled into the back section. Instead of simply breaking up the muzzle blast and allowing the majority of the escaping gas to shoot forward, this muzzle device contains the majority of the expanding gas and redirects it rearward until diffused through the smaller flash holes at the back muzzle device body. The front sight is attached on top of the device. This design not only limited the amount of perceived muzzle flash, but also reduced felt recoil and did not increase perceived noise like other compensators.

Just picture an alternate scenario where the AR-10 platform in this configuration was chosen over the M-14. What would the modern day small arm look like?

Photo credit: Michael Fullana IMT