The .45 Auto pistol is a single-action, semi-automatic, magazine-fed handgun that utilizes .45 Autoammunition. While the .45 AP improved sights modification was cut from the game, the sights are still present on the weapon's default model (pre- and post-modified versions). This gives the .45 Auto pistol luminescent sights, and as such, it is very effective in caves and dark areas.
Furthermore, it is considered an improved holdout weapon and can be taken into weapon-free locations with a Sneakskill of 50 or greater. It also has the highest base damage of any silenced holdout weapon once the AP silencer mod has been added.
The .45 Auto pistol can fire a total of about 745 standard rounds, the equivalent of 107 reloads, from full condition before breaking. When modded with the heavy duty slide, it can fire a total of about 1,120 standard rounds, the equivalent of 160 reloads, from full condition before breaking.
.45 Auto pistol improved sights – It appears as though there may have been an "upgraded iron-sight" mod available for this weapon but it was cut from the final release, and the weapon's default model uses them instead.
It can be purchased from Joshua Graham. Two or three of them will reappear in his inventory after he arrives at the Sorrows' camp.
Although Graham is seen inspecting countless amounts of these pistols when talking with the Courier for the first time, only four in poor condition can be stolen from Joshua Graham's desk in Angel cave.
Some of these are used by tribals in Zion.
There is one in good condition in a footlocker behind Joshua Graham in Angel Cave.
According to Joshua Graham, it is based on a nearly 400-year-old design and receiving one is a New Canaanite rite of passage.
Behind the scenes
The pistol's firepower was improved to make it more in line with player expectations, rather than reality.
Because weapon details might have to differ from their real world counter parts for technical reasons, which can result in pedantry over the inconsistencies between real world weapons and their in game counterparts, the .45 auto pistol is one of many weapons given a functional name to avoid specific designations used by manufacturers or the military. Joshua Sawyer described this as the reason the .45 auto pistol appears rather than the M1911.
If both mods are attached and you use a weapon repair kit on it, the weapon stops degrading from use and can continue to be repaired past 100% increasing its value and condition. [verified]
Sometimes, when both modifications are attached to the .45 Auto pistol, it will not show in first person or third person view while in the Mojave Wasteland. [verified]
If loading a saved game from the main menu in which you have the .45 Auto pistol equipped and drawn, the reload animation takes twice as long as normal. This can be solved by switching to another weapon, then back again. [verified]
Sometimes when aiming down the sight while in the first-person view, the gun will disappear entirely. Switching to another weapon, then back seems to fix the issue. [verified]
Sometimes, when ED-E repairs the weapon with both modifications, the condition will actually degrade instead of improving. [verified]
.45 Auto pistol with the heavy duty (HD) slide modification
.45 Auto pistol with the silencer modification
.45 Auto pistol with both modifications
.45 Auto pistol with the non-playable iron sights
.45 Auto pistol with the heavy duty (HD) slide modification and the non-playable iron sights
.45 Auto pistol with the silencer modification and the non-playable iron sights
.45 Auto pistol with all the modifications and the non-playable iron sights
↑Joshua Sawyer on Something Awful forums Acebuckeye13: "The Devs in New Vegas actually tried to balance weapons based on the power of their real-world calibers, which is why they buffed 10mm, added 9mm as a replacement low-tier ammo, and got rid of .32 entirely (Because it was completely ludicrous)." rope kid (Joshua Sawyer): "The exception to this was .45 Auto (ACP). To make it appealing as a mid-tier semi-auto caliber between 10mm and 12.7mm with a 7 round magazine, I had to give it TRUE TALES OF THE 1911 stats. I still feel slightly bad about it, but people like Last Man Standing-style .45s that throw guys 20' through the air, so..."'
↑Joshua Sawyer on the Bethesda forums Joshua Sawyer: "In general, I prefer to give weapons functional names and avoid getting wrapped up in specific designations used by manufacturers or the military. Because our weapons must, for technical reasons, occasionally differ functionally from the weapons upon which they are based (different caliber, charging handle placement, receiver height, stock shape/length, etc.) giving them a more utilitarian name helps negate some of the potential pedantry over those deviations. There are no AR-15s, Colt Commandos, Browning Hi-Powers, BFRs, M1 Garands, Winchester 1886s, 1887s, or 1892s in Fallout: New Vegas -- just Service Rifles, Assault Carbines, 9mm Pistols, Hunting Revolvers, This Machine, Brush Guns, Lever-Action Shotguns, and Cowboy Repeaters. That's also why there are no M1911s or Thompsons in Honest Hearts, but you'll find plenty of .45 Auto Pistols and .45 Auto Submachine Guns."