It uses 9x19 rounds which are quite easy to obtain nearly anywhere, however it doesn't have much firepower and is advised only to be used as a sidearm, not a primary weapon. The gun and its ammo are very lightweight, making it a preferable handgun for one who doesn't use a handgun frequently. Cannot mount a silencer in the unmodified game.
In Clear Sky it's less available, it must have been too expensive at the time and too hard for traders to obtain.[source/verification needed] It can be upgraded by almost every technician, it's cheap to upgrade and easy to maintain however albeit susceptible to damage when being fired at a rapid rate but has less chances of the weapon jamming. This is also the only 9x19mm caliber pistol that can be mounted with a silencer.
The Walker P9m is the standard sidearm of lower ranking members of the Monolith faction, it is commonly found in Limansk and in the Limansk Hospital. Some veteran Freedom snipers using SVUs also use this weapon as a sidearm.
It can only be bought from Mitay after joining the Duty faction, although one can be found in the rear of a truck next to a body and an RGD-5 Grenade, as well as a Medkit in a metal case, on the road in the middle of Agroprom on the left fork leading to the Duty base. This is not as easily obtained as it seems, however, as there is no crate from which to mount and then enter the rear of said truck, requiring a different plan of action to be taken. Alternatively, if you managed to save Sergeant Cheersov near the hole that leads into the Agroprom Underground, he will give you the coordinates of a stash containing the pistol and 1 box of 9x19mm FMJ rounds in exchange for 900 rubles, the stash is located in the final spiral staircase at the bottom inside a toolbox-like object.
You can also get this weapon free of charge by joining Freedom and wiping out the Duty base. Along with the P99, you'll get a FreedomExoskeleton, a Dragunov SVD, 15000 RU, and lots of ammo.
This weapon also appears in Call of Pripyat. It is capable of three-round burst-fire with a 3rd tier upgrade and is one of the better pistols in the game due to it's light weight, high durability, large magazine capacity, and favorable stats. The only disadvantage is quite disappointing damage.
Walker P9m can be fitted with a silencer but must be upgraded to do so.
The Walker also, as mentioned earlier, has the highest magazine capacity for any handgun in the game with a stock 16-round magazine.