Knights Armament KAC SR-15 CQB E3 Mod 2 11.5" M-LOK Upper Receiver Group

The Knight's Armament SR-15 E3 Mod 2 CQB 11.5" M-LOK Upper Receiver Group — a new, unfired KAC take-off featuring the E3 round-lug bolt, URX 4 M-LOK handguard, and 5.56 NATO cold hammer-forged chrome-lined barrel. This is one of the most sought-after short-barrel uppers Knight's produces.

• KAC-manufactured SR-15 E3 Mod 2 CQB upper — new, unfired take-off from a complete rifle
• 11.5" cold hammer-forged, chrome-lined barrel, 1:7 twist, 5.56 NATO
• URX 4 M-LOK handguard — free-floated, the current-generation KAC rail
• E3 round-lug bolt design for extended bolt life
• 3-Prong Flash Eliminator — also compatible with KAC's 5.56mm QDC signature-reduction suppressors

What the SR-15 E3 Mod 2 CQB is

Knight's Armament Company (KAC) builds some of the highest-tolerance small arms in the US industry, with decades of military and LE fielding behind the SR-15 and SR-25 lines. The SR-15 E3 Mod 2 is KAC's current-generation 5.56 short-barrel carbine upper. The "E3" refers to the round-lug bolt and matching barrel extension — KAC's engineering fix for the fatigue-crack failure mode common to 7- and 8-lug bolts under sustained high round counts. The round-lug geometry distributes locking forces more evenly, which is why KAC and independent testers report significantly extended bolt service life on E3 rifles.

"Mod 2" designates the current URX 4 M-LOK handguard generation. Prior SR-15 uppers shipped with URX 3 or URX 3.1 rails; Mod 2 is the M-LOK configuration. The URX 4 free-floats the barrel, carries the KAC-typical slim profile, and accepts a 5-slot M-LOK rail section at the 12 o'clock front (included).

Specifications

• Barrel: 11.5", 1:7 twist, cold hammer-forged, chrome-lined
• Caliber: 5.56mm NATO
• Bolt: KAC E3 round-lug BCG
• Charging handle: KAC ambi
• Handguard: URX 4 M-LOK
• Muzzle device: KAC 3-Prong Flash Eliminator (QDC-compatible)
• Buffer: HH heavy buffer
• Sights: Front and rear Micro BUIS included
• Weight: 3.8 lb
• OAL: 20.5"
• Part: KM-31963

Condition and sourcing

Charlie's receives these as both new-in-box and as new take-offs from complete KAC rifles. In current stock, most are recent take-offs — Knight's has been slow to issue component-only parts in recent years, so the upper is pulled from a new rifle, test-fired once at KAC, and otherwise untouched. No factory box. Rail covers not included. Pictures may show BUIS/optic configurations that are not part of this SKU — no optic is included.

NFA notice: This is a short-barrel upper. Building it onto a registered SBR lower or a pistol configuration requires compliance with federal NFA rules and your state's laws.

ITAR notice: This upper contains restricted parts. It cannot be exported or transferred to non-US Persons without State Department authorization.

Charlie's deals in the real McCoy — this is KAC-new, not a commercial SR-15 lookalike. Order yours today and build the short-barrel SR-15 the right way.