Benelli Shotguns: From the 121 and Super Black Eagle to the M3 and M4

Key Takeaways

• The Model 121 established Benelli’s commercial inertia-operated shotgun lineage in 1968.
• The Montefeltro introduced the rotating locking head later associated with the M1, M2, and Super Black Eagle.
• The M3 combines inertia and pump operation, while the M4 uses Benelli’s dual-piston ARGO gas system.

Benelli Armi’s development is unusually coherent for a firearms manufacturer. From the Model 121 through the Super Black Eagle, M1, M2, and M3, most of its important semiautomatic shotguns grew from one operating principle: Bruno Civolani’s inertia system. The M4 later established a separate, gas-operated branch designed for military service.

The Civolani System and Model 121

The Benelli brothers founded Benelli Armi S.p.A. in Urbino, Italy, in 1967. That year, Civolani developed the inertia-operated mechanism that would define the company’s semiautomatic shotguns. Benelli built its Urbino factory and began firearms production the following year. Its first major shotgun, the 12-gauge Model 121, entered production in 1968.[1]

The original system used three principal bolt components: a locking head, a heavier bolt body, and a stiff spring positioned between them. Upon firing, the shotgun recoils while the bolt remains locked. The bolt body’s inertia compresses the spring; as the spring expands, it drives the bolt body rearward, unlocks the action, extracts and ejects the fired case, and permits the next cartridge to be chambered.[2]

Unlike a gas-operated action, the mechanism does not divert propellant gas through ports in the barrel. This arrangement limits the amount of combustion residue entering the operating system and reduces the number of moving parts required around the barrel and fore-end. It does not, however, eliminate the need for proper cleaning, lubrication, inspection, or suitable ammunition.

SL80 and the Move to Smaller Gauges

Benelli introduced its first 20-gauge semiautomatic, the SL201, in 1973. The SL80 series followed in 1974 and included the 121, 123, Special 80, and Extra Lusso. Benelli offered those models in hunting, target-shooting, and slug configurations.[1]

These early guns are important because they document the first commercial phase of Benelli’s inertia system. They also predate the rotating bolt head that became one of the most recognizable features of later Benelli shotguns. On an early example, the precise model designation, gauge, barrel configuration, serial number, proof marks, and importer’s mark matter more than a broad family resemblance. Parts may have been exchanged during decades of use, so configuration should be established from the firearm itself and, when available, contemporary records.

Montefeltro and Super 90

The mechanism changed substantially with the Montefeltro in 1983. According to Benelli, this was its first inertia-operated shotgun fitted with a rotating locking head. The company also replaced the earlier open-topped receiver arrangement with a wraparound receiver and a removable trigger group.[3]

The Super 90 followed in 1985, adding a magazine cutoff and a shim system for adjusting drop and cast. In 1987, Benelli introduced the Raffaello family, combining the styling and general architecture associated with the 121 lineage with the rotating-head system developed for the Montefeltro.[3]

These changes established the mechanical pattern familiar on subsequent Benelli semiautomatics: a bolt body containing the inertia spring, a rotating head that locks at the breech, and a separate return spring that drives the bolt forward after cycling.

M1 and M2

The M1 Super 90 brought this architecture to hunting, sporting, slug, and tactical configurations. Contemporary retrospective accounts place its introduction in the mid-1980s and identify it as a direct predecessor of the M2.[4] Because M1 production included different gauges, barrel lengths, finishes, stocks, sights, and intended uses, the designation alone does not establish a particular gun’s original configuration.

Benelli introduced the M2 in 2004 as the M1’s successor. It retained the inertia-operated, rotating-bolt mechanism while incorporating features such as the ComforTech stock and Crio barrel-and-choke system on applicable versions.[4] The M2 subsequently appeared in field, slug, tactical, competition, and specialized hunting forms.

The distinction between an M1 and an M2 is therefore evolutionary rather than conceptual. Both belong to the Super 90 lineage, but their furniture, barrel systems, controls, finishes, and factory configurations should not be treated as interchangeable when evaluating an individual firearm.

The Super Black Eagle

Benelli introduced the original Super Black Eagle in 1991. The company identifies it as the first commercially offered 3½-inch semiautomatic shotgun on the United States market.[1] Its principal achievement was adapting the inertia system to a 12-gauge action capable of handling the 89 mm, or 3½-inch, Super Magnum cartridge.[3]

The third generation arrived in 2017 as the Super Black Eagle 3.[1] In its 3½-inch 12-gauge form, it retained the inertia action while adding an Easy-Locking Bolt System, enlarged controls, revised loading geometry, and stock-fitting adjustments. Benelli’s Easy-Locking system uses a spring-loaded detent to encourage the rotating head into full engagement if the bolt has been eased forward or slightly displaced.[5]

Certain SBE 3 configurations use the ComforTech 3 stock and Combtech cheek pad. Factory literature also specifies adjustable drop and cast through a shim system. These features vary by model and stock configuration; they should be confirmed against the exact catalog number rather than assumed from the SBE 3 name alone.[5]

M3: Inertia and Pump Operation

The M3 Super 90 combines two operating modes in one firearm. In semiautomatic mode, it functions through Benelli’s fixed-barrel inertia system. Rotating a selector ring at the fore-end converts the gun to manually operated pump action by coupling the fore-end to the bolt assembly.[6]

The pump setting allows the action to be cycled manually when a cartridge does not produce sufficient recoil to operate the semiautomatic mechanism or when the user otherwise requires manual control. The M3 is consequently neither a conventional pump shotgun with an added self-loading feature nor a gas-operated convertible. Its semiautomatic mode remains inertia operated.

M4 and the ARGO System

The M4 departed from Benelli’s established inertia formula. Developed in 1998 for a United States military requirement, it uses Benelli’s Auto-Regulating Gas-Operated system, commonly abbreviated ARGO. Benelli records the M4’s selection by the United States Marines in 1998; the military version subsequently received the M1014 designation.[1][7]

The M4 is a 12-gauge, tubular-magazine-fed semiautomatic with a rotating bolt head and two locking lugs. Its ARGO system employs two short-stroke gas pistons positioned near the chamber. Gas tapped from the barrel acts on the pistons, which bear directly on the bolt carrier assembly to cycle the action.[8]

Locating the ports close to the chamber exposes the system to relatively hot, high-pressure gas. A regulating function vents excess gas rather than applying the full available pressure to the operating components. The design also avoids the long action bars found in some gas-operated shotguns.[7]

The M4 therefore represents a genuine second branch of Benelli shotgun development. It shares the rotating-bolt concept seen in the company’s later inertia guns, but its operating energy comes from propellant gas rather than the relative movement of the firearm and bolt body under recoil.

Understanding the Lineage

Benelli’s shotgun history is best read as a sequence of identifiable mechanical developments. The 121 established the commercial inertia system. The SL201 and SL80 expanded the early platform. The Montefeltro introduced the rotating locking head, and the Super 90 architecture led to the M1 and M2. The Super Black Eagle extended the system to the 3½-inch 12-gauge cartridge, while the M3 combined inertia operation with a selectable pump mechanism. The M4 then applied a short-stroke, dual-piston gas system to a military semiautomatic shotgun.

For collectors, that chronology is a starting point rather than a substitute for examining an individual firearm. Model markings, serial number, proof marks, barrel and chamber markings, importer identification, furniture, finish, and mechanical configuration must be considered together. A Benelli’s historical position can be described by its model family; its originality and provenance can be established only through evidence specific to that gun.

Frequently Asked Questions

When was Benelli Armi founded?
The Benelli brothers founded Benelli Armi S.p.A. in Urbino, Italy, in 1967.

How does Benelli’s inertia system work?
Recoil compresses a spring between the locked bolt head and bolt body. The spring then drives the action rearward to unlock, extract, eject, and reload.

Why is the Super Black Eagle historically important?
Introduced in 1991, it was the first commercially offered 3½-inch semiautomatic shotgun on the U.S. market, according to Benelli.

Can the Benelli M3 operate as both a semiautomatic and a pump shotgun?
Yes. A selector at the fore-end switches the M3 between inertia-operated semiautomatic fire and manual pump operation.

Is the Benelli M4 inertia operated?
No. The M4 uses Benelli’s ARGO system, which operates through two short-stroke gas pistons positioned near the chamber.

Sources

1. Benelli Armi S.p.A., “Benelli’s History,” official company chronology.
2. Benelli Armi S.p.A., “The Inertial System,” March 16, 2022.
3. Benelli Armi S.p.A., “The History of the Benelli Inertial System,” June 30, 2022.
4. Phil Bourjaily, “Benelli M2 Shotgun Review: The Ultimate Mid-Priced Semiauto,” Outdoor Life, June 18, 2025.
5. Benelli USA, “Legendary Benelli Super Black Eagle 3 Continues to Dominate the Skies with Addition of 20-Gauge and 3-Inch 12-Gauge Shotguns,” January 19, 2021.
6. Benelli Armi S.p.A., “M3 Convertible Semi-Auto/Pump Shotgun Product Manual,” official operating manual.
7. Benelli USA, “A.R.G.O.,” official technical description.
8. Benelli Armi S.p.A., “M4 Tactical Shotgun Product Manual,” official operating manual.