The Infiltrator is a silenced and scoped, stockless, and shorter assault rifle. It has the lowest DAM and DPS of any weapon in the assault rifle class. However, the integral sound suppressor permits repeated sneak attacks, while the scope permits enhanced spotting.
Despite this weapon's scope, it still suffers from the typical inaccuracy of assault rifles, struggling to put together a tight grouping at minute distances. Combined with the fact that each bullet doesn't hit particularly hard, this weapon is not viable for long-distance fighting, especially on higher difficulties, the Infiltrator's low damage outweighs its firing volume benefits.
However, due to the silenced nature of the gun, any player character with a high Sneak skill who maneuvers to a good position to take out softer targets like Raiders will benefit from the weapon. The same 24-round magazine, however, makes following up VATS-attacks without taking damage or alerting further enemies difficult as most of the ammo would have already been lost.
The Infiltrator can fire a total of about 1429 rounds, the equivalent of 60 reloads, from full condition before breaking, roughly 429 rounds more than the Perforator, and 177 rounds more than the assault rifle.
Perforator - A unique version of the Infiltrator, it offers higher damage but a slower rate of fire.
Sim version - A sim-only version of the weapon which differs only in health (essentially non-degrading). It features a cleaner, less-battered texture with fresh wooden and darker metal areas than its wasteland counterpart.
Wanda - A unique R-91 assault rifle that was cut from the final game, and only can be obtained using console commands.
Alloy steel assault rifle - A variant named "alloy steel assault rifle" can be found in the data files for Operation: Anchorage. It uses the Anchorage-specific texture for the weapon, but aside from name and appearance is identical to the standard R-91 assault rifle. It is likely the weapon was intended to be placed in the armory with other "wasteland" versions of weapons found in the Anchorage sim, most of which were cut from the final version of the add-on; as such the weapon can only be accessed through the use of console commands.
At the entrance into the Pitt's Downtown area, past the Pitt bridge, two Pitt raiders and their leader Mex stand guard. They all carry Infiltrators. Note that Mex can also spawn with a normal raider weapon, but will carry the Infiltrator regardless.
Fallout: New Vegas includes a brief appearance of the Infiltrator, seen on two of the walls of the "hidden" weapons room in Mick & Ralph's. They are non-interactive static meshes acting like a decoration.
The Infiltrator's magazine has the same capacity as its standard counterpart, yet it is noticeably larger.
The Infiltrator's texture file includes a fully textured stock in the same black paint as the other metal parts, suggesting at one point the weapon was to have a stock.