The Multifunctional Assault Rifle: Future Standard or Unrealistic Dream?

Modern infantry squads often carry a mix of weapons – assault rifles, light machine guns, and designated marksman rifles (DMRs). Each excels in its own role, but this diversity comes at a cost: more training requirements, no magazine interchangeability, and more logistical complexity in the field.

But what if one weapon could do it all?In this blog, I take a closer look at the multifunctional assault rifle – a single platform designed to combine the firepower, accuracy, and versatility of all three.

My First Encounter with the Concept

When I began my compulsory military service in 1983, I was issued my personal service rifle – the 7.5 mm Sturmgewehr 57 (Stgw 57). It was developed by SIG under the designation AM55 and was later commercialised in various versions as the SIG SG 510.

The Stgw 57 was designed as a multifunctional assault rifle, with the following capabilities according to the field manual:

• Rifle: effective up to 600 m.

• Anti-tank: with shaped-charge rifle grenades up to 100 m.

• Grenade launcher: shrapnel or smoke rifle grenades up to 250 m in direct fire; shrapnel rifle grenades up to 400 m in indirect fire.

• Bayonet for close combat.

Indirect fire with shrapnel rifle grenades

Needless to say, the Stgw 57 was not an effective multifunctional assault rifle. Here are some observations:

• The Stgw 57 was a precise weapon, but with a loaded weight of 6.6 kg, most shooting was done prone on the bipod (in the middle position) or supported (terrain). Unsupported stances were almost never used due to the weight and poor ergonomics.

• Moving the bipod to the forward position was intended to better stabilise the Stgw 57 when used as an automatic rifle. In practice, almost no one could keep bursts within the intended 4 ‰ dispersion.

• The 1.16 kg shaped-charge rifle grenades had enormous (and I mean enormous) recoil, and most shooters were afraid of it, resulting in poor shooting performance.

• The Stgw 57, however, excelled as an indirect fire grenade launcher with shrapnel rifle grenades.

For the record, the negative recoil experiences with the rifle grenades were a decisive factor in choosing a 40 mm grenade launcher for the 5.6 mm Stgw 90 instead of rifle grenades.

Special Forces Trials

During my time in the Special Forces Command, I experienced the concept of using an assault rifle as a squad automatic weapon. The advantage of having a lightweight weapon with the same magazines for all weapons in the squad is obvious.

At that time, we were using the 5.6 mm Stgw 07 (SIG SG 553 LB), but its handguard length was inadequate for that role. We conducted trials with a SIG SG 551 LB (longer handguard and 17.8-inch barrel), equipped with a bipod and a 3.5X ACOG scope.

The shooting tests in bursts and rapid single fire were excellent and met the requirements. Unfortunately, the weapon could not sustain the required number of magazines and rate of fire without cook-off, and the project was terminated.

The US Marine’ Approch!

So, is the concept of a multifunctional assault rifle feasible? Yes – and, as so often, the US Marines led the way.

In 2010, they fielded the M27 Infantry Automatic Rifle (IAR) as a replacement and supplement for their M249 light machine guns. The M27 IAR is essentially a standard H&K 416 with a 16-inch barrel – the best compromise in barrel length for the 5.56 × 45 mm – and it met the cook-off requirement (36 rounds per minute for 16 minutes and 40 seconds) despite being a closed-bolt system.

In 2017, they introduced the M38 designated marksman rifle, which is basically an M27 IAR fitted with a Leupold TS-30A2 Mark 4 MR/T 2.5–8×36 mm scope.

By 2018, they began transitioning from the M4 to the M27, and in 2020/21 they replaced the 3.5× ACOG with the Squad Common Optic (SCO) – the Trijicon VCOG 1–8×28 – and issued the Knights Armament Company (KAC) NT4 suppressor for all M4, M27, and M38 rifles.

USMC M27 assault rifle

Conclusion

From my experience, a single, well-designed platform can deliver all three roles – rifle, squad automatic weapon, and DMR.

The light machine gun vs. squad automatic rifle debate will never end. For me, lighter weight, faster reloads, magazine commonality, and precision in single fire outweigh a higher sustained rate of fire – at least on the move. In defence? I’d still take the belt-fed LMG.

Most modern assault rifles can also serve effectively as DMRs. Equipped with a modern LPVO, an assault rifle can provide designated marksman capability. Purists will disagree, often because they envision a DMR as a “mini sniper rifle.”

Hopefully, this idea will be on the table when Switzerland starts replacing the 5.6 mm Stgw 90 (SIG SG 550) in the coming years.