The CPU Handgun is a standard-issue law enforcement pistol given to Mainframe's officers. A firearm with a relatively short barrel that is held and fired with one hand, though some Binomes used both hands on the trigger.
These guns fire rapid rounds of short-range energy bursts at their targets. The firearms can fire blanks during training, however Matrix always had the CPUs use live ammunition during training exercises held in Lost Angles.
During peace times officers rarely found themselves having to use them, though after the Web War, Mainframe was plunged into the Viral Wars against Megabyte and his ABC army, and an increasingly-insane Hexadecimal. When the firewall overloaded from Hexadecimal's assault, the CPUs failed to stop Megabyte taking over the Principal Office. Dot organized them into the Mainframe Rebellion. Small conflicts broke out all over the city, the handgun saw action during this part of the conflict even with the CPUs underground. (Megaframe)
After Mainframe crashed and restarted the CPUs turned their attentions on the infected Guardian Armada. When they invaded Mainframe to take out the Control Tower and forced the city to stay connected to the Net. The CPU guards in the tower used the handgun to defend it, but were quickly defeated by the Guardians. The infected Guardians broke thru their defenses, deleting everyone in the perimeter, before destroying the superstructure along with them inside it. (Daemon Rising)
By this time, Hexadecimals insanity was long cured by Bob but she then unexpectedly converted into a Sprite following her icon's viral scan. The nulls tried to protect her from being erased, which revived the sentience of Welman Matrix, who everyone thought was lost along with the destruction of the Twin City. The CPUs fearing yet another Nullzilla incident arrived in Kits Sector and tried to contain the null cocoon. When the cocoon began 'freaking out' the CPU guards opened fire with their handguns on the cocoon. Dot arrived and ordered them to stand down, hoping to communicate with them somehow. (Cross Nodes)
After the threat of Daemon and her Net-wide infection had passed, Matrix used Lost Angles as a training ground. However he forced the CPUs to attack him with live ammo, not blanks. The CPU officers were worried that on several occasions they nearly hit him, and even more worried at what Matrix would do to them if they didn't try to hit him. AndrAIa arrived on the island and quickly put a stop to the madness. (My Two Bobs)