http://en.wikipedia.org/wiki/M24_Sniper_Weapon_System 
 “The M24 originally came topped with the Leupold Ultra M3A 10×42mm fixed-power scope, which came with a circle-shaped mil-dot glass-etched reticle. This was later replaced in 1998 by the cheaper Leupold Mk 4 LR/T M3 10×40mm fixed-power scope with an elongated-shaped mil-dot wire reticle.[2]”