The M24 was designed to use the "long-action" version of the Remington M700 BDL. This was chosen because the Army wanted the ability to rebarrel the rifle from 7.62 NATO to the .300 Winchester Magnum cartridge if needed, which required a long action receiver. Due to using a short action cartridge in a long action receiver and magazine box, rounds must be pushed to the rear of the magazine in order to ensure reliable feeding.
The M24 originally came tapped for the Leupold Ultra M3 10×40mm fixed-power scope, which came with a circle-shaped etched-glass reticle. This was later replaced in 1998 by the cheaper Leupold Mk 4 LR/T M3 10×40mm first focal plane fixed-power scope with a mil-dot reticle.
The first number is the scope's magnification (10) and the second number in millimeters (40mm) is the diameter of the objective lens. A fixed power scope has only one magnification (e.g., 10×) and a variable power scope can be adjusted to focus between a range of magnifications (e.g., 3–9× is adjustable from a minimum power of 3× to a maximum power of 9×). The rifle itself comes with a detachable Harris 6-9" BRM-S swivel bipod unit.
The M24 SWS was to be replaced with the M110 Semi-Automatic Sniper System, a contract awarded to Knight's Armament Company. However, the Army still continued to acquire M24s from Remington until February 2010 and the M24 is being upgraded to the A2 and M24E1 standard in many cases, and continues to serve. The Army is likely to upgrade its 2,500 M24s to XM2010 Enhanced Sniper Rifle standard.