The large-framed, gas-operated N99 was selected as the standard issue conventional sidearm of the United Statesmilitary, following the phaseout of the N80 in 2051. The long-barreled pistol remained in service for 26 years, until the Great War destroyed the United States. The pistol is designed to withstand the most extreme conditions, which was one of the requirements for a new service sidearm. It can also be repaired easily by anyone with even the most basic technical knowledge. This includes both clearing misfeeds and restoring a unit to working condition after long exposure to elements without maintenance.
These features also make it popular with wastelanders, who appreciate the ease of maintenance. It remains a common weapon, as even though many civilian units were ruined, they can easily be restored by anyone with some repair knowledge. Even damaged units can be used reliably, though they will offer subpar performance and jam frequently. The number of manufactured pistols means that parts are easy to come by, however.
It does more damage and critical damage than regular 10mm pistols. It also has a higher value and item HP. It is obtained from Colonel Autumn's body at 100% condition.
The Colonel's 10mm can fire 575 rounds before breaking. That's about 48 magazines, which is 23 more rounds than the normal 10mm. It fires around 20 magazines or 245 rounds more than the silenced version.
This weapon is carried by Colonel Augustus Autumn during the main story. During the Waters of Life quest after the colonel supposedly "dies", you can grab his belongings as long as he falls near the door.
You must face directly towards the body with the cursor directly on the body in first person view. Once this is done, hold down the button that changes the perspective and you should be able to rotate the camera. Rotate the camera 180 degrees and you should see a "Search Colonel Autumn" message. You can also search Dad and possibly everyone in the room if they fall close enough to the wall. If it is not taken then, it will not spawn on him during the final fight during Take it Back!
↑The Lone Wanderer: "Your gun is jammed? Can I take a look at it?" Pek: "Sure, I guess. Can you fix it?" The Lone Wanderer: "Sure can. Here, just pull this back to clear the chamber." Pek: "Wow... that's... that's easy. Now at least I can shoot back at those mutant bastards. Are you ready?" (Pek's dialogue)
↑ 2.02.1Citadel terminal entries: N99 10mm Pistol: "The 10mm N99 sidearm was standard issue military gear following the phase out of the N80 in 2051. The N99 was known for its ability to survive in the harshest of conditions and in many tests, the weapon was able to reliably be restored to working condition after an extended period of time exposed to hard elements and without maintenance. The N99 proved to stand up to its claims and as a result, is one of the most common weapons found in use in the Wasteland. While many civilian weapons were ruined beyond use in the exterior conditions following the war, the N99 is commonly able to be easily restored to working order by anyone with the most basic knowledge of firearm mechanics. However, an N99 in poor condition can often deliver low target and armor penetration, frequent jamming, and greatly reduced accuracy. Fortunately, the weapon was produced in great numbers and units are available for replacement parts."