AR-10 patterns, explained: DPMS vs Armalite, and why it matters
Before you buy an AR-10, know which pattern it is. Magazines, uppers, and parts do not cross.
New AR-10 buyers run into a fact that AR-15 buyers never do: **"AR-10" is not one standard.** It is a colloquial umbrella term for two and a half non-interchangeable rifle patterns that look nearly identical from the outside and share almost nothing inside.
If you are about to buy your first .308-class AR, this is the single most important thing to know before you spend money.
## The two main patterns
**DPMS LR-308 pattern** is by far the more common civilian standard. Built by DPMS starting in the early 2000s, it's what Palmetto State, Aero Precision, BCM, Ruger SFAR, Savage, CMMG, and most of the AR-10 makers the average civilian has heard of use. Magpul PMAG SR25/LR308 magazines, Magpul D-60 drums, and most aftermarket magazines are built for this pattern.
**Armalite pattern** (sometimes called "AR-10A") is the older, legacy Armalite-specific pattern. It exists, Armalite still makes guns to this pattern, and it is *not* compatible with DPMS magazines or receivers.
Uppers, lowers, magazines, bolt carriers, and barrel extensions do not cross between the two patterns. A DPMS-pattern upper will not sit on an Armalite-pattern lower. A PMAG SR25 will not feed from an Armalite-pattern magwell.
## And then there's SR-25
**Knight's Armament SR-25** is a proprietary pattern that shares some characteristics with DPMS but runs its own magazines — **SR-25 PMAGs** are the civilian-purchasable version. Most modern "DPMS-pattern" rifles accept SR-25 PMAGs, which has made SR-25 the de facto magazine standard for civilian DPMS-pattern guns even though the rifles aren't SR-25s.
## How to tell which you have (or are buying)
Three quick checks:
1. **Ask the manufacturer.** Every AR-10 maker publishes the pattern. If the spec sheet doesn't say, assume DPMS and verify with the maker. 2. **Check magazine fit.** If a Magpul PMAG SR25 inserts and locks up cleanly, it's DPMS-pattern. If the mag doesn't fit at all, it's probably Armalite-pattern. 3. **Look at the takedown pin geometry.** DPMS-pattern pins are slightly offset vs Armalite — obvious once you've seen both, invisible until then.
## Why this matters
Because a DPMS-pattern upper on an Armalite-pattern lower is not a rifle, it is a door stop. Because Armalite-pattern magazines at a gun show are not magazines for your DPMS rifle, they are a $40 mistake.
When we say "make sure you know which pattern your rifle is before you buy anything" — magazines, a new upper, a spare lower, even accessories — this is what we mean. The AR-10 ecosystem looks like the AR-15 ecosystem and isn't.
For a first AR-10, the safe recommendation is: **DPMS-pattern, takes SR-25 PMAGs, from a reputable maker** (Aero, BCM, PSA, Ruger SFAR, Savage MSR-10, CMMG). Everything after that is specialization.