Knights Armament SR-15 IWS KAC Complete Lower - Virgin with Geissele Trigger

KAC SR-15 IWS Ambidextrous Lower Receiver, Virgin 

If you have spent any time around serious AR builders, you already know the conversation eventually turns to the Knight's Armament SR-15 lower. It is one of the few AR-pattern receivers where the ambidextrous controls were designed into the forging from the start, not bolted on after the fact. Knight's built the magazine release and bolt release to work from either side of the rifle, and the result is a lower that feels as natural in the left hand as it does in the right.

The hard part has always been getting one. KAC rarely sells SR-15 lowers on their own, and most complete lowers you see on the secondary market are take-offs, pulled from finished rifles. This one is different. The receiver came to us directly from Knight's as a lower, never assembled into a rifle, and our sister company Potomac Armory built it into the complete assembly you see here, with components we would choose for our own rifles.

Highlights

• Genuine KAC SR-15 IWS Receiver — The real Knight's Armament forging, with factory ambidextrous magazine-release and bolt-release architecture
• Virgin From Knight's — Never assembled as a rifle; ships with a Charlie's certificate of provenance
• Geissele G2S Two-Stage Trigger — Clean take-up, a crisp wall, and a predictable break
• Schmid Ambidextrous Safety — Military-grade selector from the maker of Colt's lower parts
• KAC Gray Receiver Extension — Six-position carbine tube with the KAC castle nut and KAC QD end plate
• Geissele Super 42 Buffer Spring with H1 Buffer — Smoother cycling, longer service life
• Mil-Spec A2 Grip — The classic, honest pistol grip
• Pistol-Build Eligible — Because it left Knight's as a lower, you have the option

Why the SR-15 Lower Is Worth It

Most "ambi" AR lowers are ordinary receivers with a handful of aftermarket parts added. The SR-15 is not that. Knight's machined the receiver to accept its own bilateral bolt release and ambidextrous magazine release, so the controls sit where your hands expect them and function with factory reliability on either side. For a left-handed shooter, or anyone who trains to shoot from the support side, that difference is felt on every reload.

This is the classic SR-15 IWS architecture, the generation that made the SR-15 Mod 2 a benchmark carbine. If you are building around that lineage, or simply want the lower that started the conversation, this is the one.

Built by Potomac Armory, the Way We Would Build It

Potomac Armory took this virgin receiver and outfitted it with parts chosen on purpose, not on price.

The Geissele G2S is a genuine two-stage trigger built on Geissele's reputation for durable, service-grade fire controls. The first stage takes up the slack, the second breaks cleanly off a defined wall, and the whole thing works as well behind a 10.3" CQB upper as it does behind a 16" general-purpose carbine. It is a versatile trigger for a versatile lower.

Out back, we kept it Knight's. The KAC gray receiver extension, KAC castle nut and KAC QD end plate give you the correct KAC appearance and a flush QD sling point at the receiver. Inside the tube, we installed Geissele's Super 42 braided buffer spring with an H1 buffer, a combination many builders consider the best all-around upgrade for a 5.56 carbine. The braided spring cycles more smoothly and quietly than a standard spring and holds its tension longer, and the H1 adds a little mass to settle the action.

For the safety, we chose a Schmid ambidextrous selector. Schmid makes lower parts for Colt and a long list of military-grade rifle makers, and this is the same pedigree you would find on a government-issued carbine. The grip is a mil-spec A2, simple, proven and easily swapped if you have a favorite.

Your Stock, Your Choice

This lower ships with the receiver extension installed and no stock. That is deliberate. Whether you want a B5 SOPMOD for a clone build, a Magpul CTR for everyday use, or a KAC stock to complete the look, you get to finish it your way.

Virgin Provenance and Pistol Eligibility

This receiver arrived at Charlie's from Knight's Armament as a lower and was never assembled as a rifle. You will receive a certificate from Charlie's stating that the lower left the Knight's factory as a lower, which means it can be built into a pistol configuration, if so desired, in addition to a rifle or a Form 1 SBR.

To be clear about what this is: it is a genuine Knight's Armament SR-15 receiver, assembled by Potomac Armory, not a factory-assembled KAC lower. We think that is exactly what makes it special.

Technical Specifications

FFL TRANSFER REQUIRED: This is a serialized firearm receiver and must ship to a licensed FFL. State and local restrictions may apply. Buyer and receiving dealer are responsible for determining lawful transfer and final configuration.

CANNOT SHIP TO CALIFORNIA: SR-15 is banned by name.