Manufactured by civilian defense contractor Stent Security Solutions, the R91 assault rifle is a conventional design chambered for 5.56mm ammunition. Employing a roller delayed blowback system, it is a very sturdy design, with simple iron sights that consist of a rotary rear drum and hooded front post, a fire selector switch with three settings (safe, fully automatic fire, single shot), and a flash suppressor. The final touch is the wooden stock and handguard.
The R91 was manufactured by Stent as part of its R series, superseding the manufacturer's own M series of combat assault rifles in the early 21st century. While other models and variants were developed, the R91's combination of ruggedness, firepower, and low manufacturing costs resulted in its adoption as an assault rifle of the National Guard and issuance to troops on the Anchoragefront.
The number of working units is particularly high in the Capital Wasteland, as the National Guard units deployed there used it widely. It remains a popular sight among the inhabitants of the region, particularly slavers and raiders, though it is also available for purchase from traders and weapon dealers.
This weapon is the carbine variant of the R91 assault rifle. Its modifications, including an extended box magazine, suppressor, scope, and lack of stock, suggest it was created to be used for special operations forces. The weapon fires 5.56mm rounds and utilizes a 24-round magazine.
Despite its scope, the weapon still suffers from the typical inaccuracy of carbines at long-range combat, limiting its suitability only for short and mid-range combat. It is one of the favored weapons of the raiders in The Pitt and in 2281, Mick is known for having one in his secret collection in Freeside.
The Infiltrator is a suppressed and scoped assault rifle; shortened from its lack of a stock. It is a second-tier, special purpose automatic firearm. It has the lowest DAM and DPS of any weapon in the assault rifle class but the integral sound suppressor permits repeated sneak attacks, while the scope permits enhanced spotting (though not necessarily accuracy). The Infiltrator's AP cost, spread, magazine capacity, and critical multiplier are identical to that of assault rifles.
Despite this weapon's scope, it still suffers from the typical inaccuracy of assault rifles. Combined with the fact that each bullet doesn't hit particularly hard, this weapon is not viable for long distance fighting. On higher difficulties, the Infiltrator's low damage outweighs its firing volume benefits. However, due to the silenced nature of the gun, one can get several sneak attack criticals on a group before they know what hit them.
An Infiltrator can fire 1424 rounds, or about 59 magazines, before breaking. That's 427 rounds more than the Perforator, and 177 rounds more than the assault rifle.
Fallout: New Vegas includes a brief appearance of the Infiltrator, seen on one of the side walls of the "hidden" weapons room in Mick & Ralph's. It is a non-interactive static mesh acting like a decoration.