AR-10 (.308)

Overview

"AR-10" refers both to a specific historical rifle and, in modern American usage, to an entire family of large-frame, AR-pattern semi-automatic rifles chambered in .308 Winchester / 7.62x51mm NATO and similar cartridges. The original ArmaLite AR-10 was a 7.62x51mm battle rifle designed by Eugene Stoner in the mid-1950s; its scaled-down derivative became the AR-15 and ultimately the U.S. military's M16. Today, large-frame ARs built to handle full-power .308-class cartridges are commonly called "AR-10s," even though the name "AR-10" is a registered trademark of ArmaLite, Inc. Because the modern category grew up without a single governing standard, these rifles are split into two principal, largely non-interchangeable receiver patterns — the ArmaLite pattern and the DPMS/SR-25 (LR-308) pattern — which is the single most important compatibility issue for buyers and builders. This entry describes the platform as a category rather than one specific SKU.

History & Background

The ArmaLite AR-10 was designed by Eugene Stoner and developed by ArmaLite, then a division of the Fairchild Aircraft (Engine and Airplane) Corporation. First prototypes of the 7.62mm AR-10 emerged between 1955 and early 1956, and the rifle was introduced in 1956. It was an innovative design for its day: a lightweight, air-cooled, gas-operated rifle using a straight-line (in-line) barrel-and-stock layout, a forged and machined aluminum-alloy receiver, a rotating-bolt locking system, and phenolic/fiberglass composite furniture. The result was a select-fire battle rifle significantly more controllable in automatic fire and more than a pound lighter than competing infantry rifles of the era. It fed from a 20-round detachable box magazine.

In 1957 ArmaLite licensed AR-10 production to the Dutch firm Artillerie-Inrichtingen (A.I.), which manufactured the rifle and sold it to several militaries in limited numbers. Documented sales include roughly 2,500 rifles to Sudan in 1958 (which kept them in service with special forces into the 1980s) and on the order of 4,000–5,000 to Portugal around 1960, with smaller purchases by other nations. Fewer than 10,000 original AR-10s were built before A.I. ceased production around 1960, so the original rifle was never a commercial mass-market success.

The AR-10's lasting importance is as the parent design of the AR-15. In 1957 ArmaLite rescaled and modified the AR-10 to fire the smaller .223 Remington cartridge, producing the AR-15; ArmaLite sold the rights to both rifles to Colt in 1959, and the further-modified AR-15 (in 5.56x45mm NATO) was adopted as the M16. The "AR" prefix comes from "ArmaLite," the company that originated the designs — not from "assault rifle."

The modern AR-10 is essentially a revival of the name on a new design. In 1995 Mark Westrom acquired the ArmaLite brand, and the company (ArmaLite, Inc.) introduced a new semi-automatic AR-10B series beginning in 1996. Critically, this rifle was not built from the 1950s drawings — it was based on the scaled-up AR-15A2 architecture, enlarged to handle the 7.62x51mm/.308 cartridge. ArmaLite holds a U.S. trademark on the "AR-10" name (in use since January 1996; registered in October 2002), which is why other manufacturers' .308 large-frame rifles are marketed under names like LR-308, SR-25, or simply "AR-10-pattern" rather than literally "AR-10."

Design & Features

A modern .308 AR ("AR-10") works on the same principles as an AR-15 but is built on a larger, heavier receiver set to contain the longer, more powerful 7.62x51mm-class cartridge. The defining practical fact of the category is the absence of a single industry standard, which produced two incompatible receiver/parts patterns.

• Operating system: Most modern AR-10-pattern rifles are gas-operated with a rotating bolt. The majority use direct impingement (gas tube), like the AR-15; a significant minority use a short-stroke gas piston. The original 1950s ArmaLite AR-10 used Stoner's gas system acting on a piston within the bolt carrier.
• Receiver: Forged or billet aluminum upper and lower receivers, larger and longer than AR-15 receivers. AR-10 and AR-15 parts are generally not interchangeable — receivers, bolt carrier groups, barrels, and magazines all differ.
• Two patterns (key compatibility issue):
• ArmaLite pattern — the original commercial AR-10 design from ArmaLite, Inc. Less common in today's parts market but still supported by some makers.
• DPMS / LR-308 / SR-25 pattern — the more widely adopted pattern, used by the large majority of modern AR-10-style uppers, barrels, handguards, and complete rifles. These patterns differ in receiver and upper dimensions: handguards, uppers, and some barrels designed for one pattern will not correctly fit the other. Mixing ArmaLite and DPMS components can produce receivers that won't mate, handguards that won't seat, or barrels that won't index — buyers should match all major components to a single pattern.
• Barrel: Typically 16 to 20 in for .308 rifles, with longer/heavier profiles common on precision builds; threaded muzzles for brakes or suppressors are typical.
• Handguard/furniture: Most modern rifles use free-float handguards with M-LOK (or earlier KeyMod) slots and a flat-top Picatinny upper, with AR-15-style collapsible or fixed stocks and pistol grips.
• Sights/optics: Generally sold without iron sights, with a continuous top rail for optics; the platform is very commonly used as a scoped semi-automatic precision or hunting rifle.
• Magazine/capacity: Detachable box magazines, typically 20-round (and 10- or 25-round) capacities. Magazines are pattern-dependent — SR-25/DPMS-pattern (often Magpul LR/SR or P-MAG .308) magazines are the most common; some ArmaLite rifles historically used modified M14 magazines.

Technical Data

Feature	Specification
Manufacturer	Many; "AR-10" is an ArmaLite, Inc. trademark. Common makers include ArmaLite, DPMS, Knight's Armament (SR-25), LMT, LaRue Tactical, SIG Sauer, Smith & Wesson, POF, Aero Precision, PSA
Model / Pattern	Large-frame AR platform; two main patterns — ArmaLite and DPMS/LR-308/SR-25
Firearm type	Semi-automatic rifle (large frame)
Action	Gas-operated, rotating bolt (direct impingement or short-stroke piston)
Caliber	.308 Winchester / 7.62x51mm NATO (most common); see chamberings below
Capacity	Typically 20 rounds (10/25-round options); pattern-specific magazines
Barrel length	Typically 16–20 in (406–508 mm)
Gas system	Rifle-length (most common on .308); also mid-length; DI or piston
Weight	Roughly 8–10 lb (3.6–4.5 kg) depending on configuration
Materials	Forged/billet aluminum receivers; steel barrel and bolt
Year introduced	Original ArmaLite AR-10: 1956; modern ArmaLite AR-10B series: 1996

Variants

The "AR-10" is best understood as two compatibility families plus the historical rifle:

• Original ArmaLite AR-10 (1956–c.1960): Select-fire 7.62x51mm battle rifle, mostly built under license by Artillerie-Inrichtingen; a collector's item today.
• ArmaLite-pattern modern AR-10: ArmaLite, Inc.'s AR-10A/AR-10B-series semi-automatic rifles and parts built to ArmaLite's own receiver dimensions; LaRue Tactical has also used the ArmaLite pattern.
• DPMS / LR-308 / SR-25-pattern large-frame ARs: The dominant modern category. Includes Knight's Armament's SR-25 (the design that effectively defined this pattern), DPMS LR-308 rifles, and the large majority of current .308 AR offerings from makers such as Aero Precision, Palmetto State Armory, POF, and others. Most aftermarket .308 AR parts are built to this pattern unless stated otherwise.
• Other notable .308/7.62 ARs of the broader class: SIG716, LMT, LaRue OBR/PredatAR, Smith & Wesson M&P10, and the military M110 (a derivative of the SR-25). Some of these use their own proprietary dimensions.

Calibers / Chamberings

• .308 Winchester / 7.62x51mm NATO — the core chambering of the platform.
• Large-frame AR receivers are also commonly chambered in cartridges sharing the .308 case head, including 6.5mm Creedmoor, .243 Winchester, .260 Remington, 7mm-08 Remington, and .338 Federal. ArmaLite has additionally offered chamberings such as 300 Remington SAUM in its AR-10-series rifles.

Intended Use

The .308 AR-10 platform bridges the gap between the light-recoiling AR-15 and a traditional bolt-action .308. Its full-power 7.62x51mm chambering makes it well suited to medium- and large-game hunting (where semi-automatic rifles are legal), semi-automatic precision and designated-marksman-style shooting, long-range target work, and tactical/defensive use that calls for more terminal energy and reach than 5.56 NATO. The 6.5 Creedmoor and similar chamberings, on the same large frame, are especially popular for extended-range precision shooting. As with the AR-15, the platform's modularity allows extensive configuration for the shooter's intended role.