Rifleman Q&A: How Do Army 'M' Numbers Work?

by
posted on April 25, 2021
** When you buy products through the links on our site, we may earn a commission that supports NRA's mission to protect, preserve and defend the Second Amendment. **
us-army-m-numbers-model-designation-f.jpg
Can you explain the significance—and formula for determining—Army “M” numbers? How is it that both the “M1911A1” pistol and the “M1” Garand were named in obviously different ways?

The methodology of determining the Model designation for U.S. military equipment was easy until the late 1920s. Prior to that time, the year in which an arm was adopted was the Model designation.

For example, the Model 1903 rifle was adopted in calendar year 1903, the Colt M1911 .45 pistol in calendar year 1911 and so forth. Among the last U.S. military arms with the year of adoption as the Model designation was the Model 1928 Thompson submachine gun.

In the late 1920s, the procedure was changed, and the Model designation was changed to M (for Model). The first service rifle adopted after the change in nomenclature was the “U.S. Rifle, Caliber .30 M1.” The first carbine adopted after the change was the M1 Carbine.

The situation becomes really cloudy when subsequent arms were adopted. For example, the next standardized service rifle after the M1 was the M14. The presumed reason for skipping from the M1 to M14 was because there were 12 rifles considered for adoption before the M14 was standardized in 1957. There was also an experimental M15 rifle, which was followed by the standardized M16.

Substantive changes to a basic model were designated by “Alteration” codes consisting of an A (followed by a number). For example, the M1911 was followed by the updated M1911A1 pistol. The second version of the M1 carbine was the M1A1. The second variation of the M16 rifle was the M16A2, and the third variant was the M16A3.

Latest

IHTOG 1854 Lorenz Jagerstutzen 1
IHTOG 1854 Lorenz Jagerstutzen 1

I Have This Old Gun: Model 1854 Lorenz Jägerstutzen

The Austrian Lorenz Jägerstutzen was a unique variant of sharpshooting rifle that made it stateside during the American Civil War.

SHIELD Sights Celebrates 40 Years of Red-Dot Optics Innovation

SHIELD Sights is celebrating its 40th anniversary, marking four decades of British engineering, innovation and contributions to the evolution of modern red-dot optics.

TX Maxed: The Taurus TXM in 5.7x28 mm and .22 WMR

Using its TX series architecture yet again, Taurus is adding the 5.7x28 mm and .22 WMR to its chambering options with the new-for-2026 TXM.

Review: Federal's 6.5 Creedmoor +Peak Ammunition

Federal’s new 6.5 Creedmoor +Peak takes a long-range staple even farther.

New for 2026: Pulsar Thermion 3 Riflescope

Pulsar’s newest thermal scope offers longer range, sharper detail and expanded functionality.

AKs In The USA: The Current State of the American AK Platform

Despite it being the primary rifle of the enemy for most of its existence, American shooters have nonetheless warmed to the AK platform, creating an unlikely love story.

Interests



Get the best of American Rifleman delivered to your inbox.