How the Army Found Its Squad Automatic Weapon: The 30-Year Search That Ended with the M249

# Overview The U.S. Army's search for a modern squad automatic weapon stretched across decades. The problem began after World War I with the Browning Automatic Rifle (BAR) and persisted through Korea and Vietnam. By the 1970s the Army recognized squads lacked a lightweight, sustained‑fire capability and launched a formal program to fix that gap.

# Why the gap mattered The BAR remained in service for years, but by Korea and Vietnam a single automatic rifle per squad proved insufficient for suppressive fire. Interim fixes—including issuing extra BARs to some squads and trying heavy weapons like the M60 at squad level—failed to deliver the desired balance of firepower and maneuverability. The M60 was effective but heavy (about 23 pounds unloaded), which constrained mobility and the amount of ammunition a gunner could carry.

# The SAW program's shift to 5.56mm Research in the early 1970s explored lighter calibers, including a 6mm SAW effort. By October 1976 the Army narrowed its focus to a 5.56mm SAW. The requirement called for a one‑man‑portable, lightweight machine gun capable of effective suppressive fire out to 1,000 meters. The program also specified new ammunition components: the M855 ball cartridge (Belgian SS109 projectile) and the M856 tracer.

# The four contenders Four designs entered formal competition:

• XM106: a modified M16 with open‑bolt action and a heavy quick‑change barrel.
• XM248: a belt‑fed 5.56mm with a rotary drive and dual gas system.
• H&K XM262: used a roller‑locked, delayed‑blowback action.

Each weapon underwent systematic evaluation across many conditions.

# Testing regimen and standards Trials covered visual and dimensional checks, parts interchangeability, firing tests, environmental exposure (salt water, heat, tropical humidity, mud, sand, dust, rain, icing), and endurance testing. Ballistic testing assessed accuracy, dispersion, penetration, and projectile performance. Reliability testing classified stoppages into three user‑clearance categories:

• Class 1: Immediately clearable (under 10 seconds).
• Class 2: Clearable (10 seconds to 10 minutes, may need tools).
• Class 3: Severe (requires armorer/maintainer).

Reliability was measured as mean rounds between failures. The XM249 exceeded specified reliability levels for Class 1 and 2 failures and nearly met targets for Class 3 under MIL‑DTC‑70446C standards. Durability expectations included a minimum 50,000‑round receiver life.

# Selection and operational confirmation The XM249's overall performance made it the clear winner of the SAW trials. An operational test at Fort Benning reinforced the laboratory results. Marine Corps experiments at Aberdeen Proving Ground produced hit‑probability outcomes that also exceeded expectations. The Army type‑classified the M249 on February 1, 1982, filling the longstanding squad‑level firepower gap.

# Where this leaves the modern force The article notes the recent introduction of the SIG M250 and frames it as the potential start of a new chapter—more accurately a reexamination of the general‑purpose machine gun role at squad and small‑unit levels. The M249's selection, testing, and fielding define the historical baseline for any current or future efforts to reshape squad suppression capability.