The magazine release button is oversized for easier operation and can be reversed to accommodate right-handed and left-handed shooters alike.
The magazine well is beveled for quick reload double-stack metal magazines, featuring a black friction-resistant finish and a FDE floorplate, are available in 10, 15, and 18-rounds capacity to comply with different laws and regulations. The slide also features deep, aggressive front and rear cocking serrations, a set of tritium sights, and a Decock-Only ambidextrous safety switch, making sure that the Beretta M9A4 is always ready for immediate deployment and use, in all conditions. GAO also found that: (1) M9 had 14 slide failures, causing injuries to four shooters (2) the contractor believes that the failures resulted from firing. The M9 won a competition in the 1980s to replace the M1911A1 as the primary handgun of the US military, beating many other contenders. It is essentially a military specification Beretta 92F, later the 92FS.
The slide of the new Beretta M9A4 can be told apart from the M9A3's by the presence of a factory interface, located just in front of the rear sight, allowing the installation of mounting plates that will accept most of the market's best known and widely available micro red dot or reflex sights – nowadays a prominent feature and a growing trend in service, defensive, and sporting pistols. The Beretta M9, formerly Pistol, Semiautomatic, 9mm, M9, is a 9x19 Parabellum pistol of the United States military adopted in 1985. This has been no easy task as the internal workings of the 92 slide have made the 'proper' low mounting of a red dot optic impossible. The gun went into service in 1985 as the M9 and was only just recently dethroned. In 2010, Beretta released an updated commercial version of the 92FS, somewhat confusingly called the 92A1. The Beretta 92 is an iconic pistol that was the standard issue sidearm for the US military for more than 30 years.
Other features of the new Beretta M9A4 include a three-slots MIL-STD 1913 Picatinny rail located in front of the trigger guard, and a full Flat Dark Earth Cerakote finish on all metal surfaces, providing superior resistance to corrosion, elements, and friction, thus reducing the need for lubrication and maintenance. Beretta answered with the M9A1 which borrows features from the 92G-SD’s frame, leaving the slide of the original M9 largely unchanged.