SI Defense Shipping Mirrored Ambi AR Receiver Sets

SI-Defense, known for their fully mirrored ambidextrous .308 receiver sets has (finally!) gotten around to releasing the baby brother mirrored control set for the standard AR-15. Like its .308 sibling, the matched receiver set is replete with fully ambidextrous magazine release and bolt catch/releases. The bolt catch/release is pulled farther back in the receiver compared to a standard AR so it can clear the ejection port door.

The Receivers are fully machined 7075-T6 aluminum with the standard black anodization. Both take standard AR parts including forward assist, trigger group, and safety/selector. Taking it a step further, the barrel extension bore is precision reamed for an excellent fit.

Receiver sets are available for $525 direct from SI-Defense and their distributors. 


Details (From SI-Defense):

  • Material: 7075-T6 Aluminum Billet
  • Finish: Deep Black hardcoat anodize
  • Patent Pending mirrored ambidextrous controls
  • Ambidextrous takedown and pivot pin locations
  • Bore is reamed for superior accuracy
  • M4 feedramps
  • Front magwell grip grooves
  • Ambi index finger grooves
  • Sleek and stylish shell deflector
  • Threaded forward assist hole
  • Quick release dust cover assembly

The SI Defense .223/5.56 receiver set is the ultimate ambidextrous receiver set. The ambidextrous bolt catch release and magazine release are mirrored identically on both sides of the receiver. These features are unique and unparalleled in the industry and were engineered to accommodate the left and right handed shooter. Special attention was given to incorporate smooth transitions throughout the receiver set, giving it a feel of confidence and reliability. The bore is machined perpendicularly and concentrically for superior accuracy. Receiver Set includes: dust cover, Ambi bolt catch, and Ambi mag release button. Unlike other ambi controls on the market our bolt catches lock back the bolt from both sides of the receiver.

Hat tip to Ben at who provided the photos. 

Nathan S

One of TFB’s resident Jarheads, Nathan now works within the firearms industry. A consecutive Marine rifle and pistol expert, he enjoys local 3-gun, NFA, gunsmithing, MSR’s, & high-speed gear. Nathan has traveled to over 30 countries working with US DoD & foreign MoDs.

The above post is my opinion and does not reflect the views of any company or organization.


  • Matrix3692

    no ambi eject like the ARX-160?

    • John

      Or the VHS-2?

  • sean

    We have one of their .308 win rifles in the store right now and its really nice. Other then the CMMG mutant its my favorite to play with right now.

  • Ben

    This is honestly one of the best thought out design changes I’ve seen for some time. This also removes the potential failings of devices like the B.A.D lever.

    I have found it frustrating that (with an ambi mag release) I have all the controls available when I shoot left handed but not when I shoot right handed. For reference I wear size M Mechanix gloves and can operate all controls without shifting my grip.

    I think there are few design possibilities too:
    1. Widen the bolt catch to increase engagement.
    2. Create a more “standard profile” lower which forgoes the more fiddly design elements (scalloped trigger finger rests, mag-well finger groves, integrated trigger guard) to reduce the price. Hell, just cast the lowers.
    3. The lower could have more material removed to reduce weight, although it is listed as 1lb on the website, so I could be wrong.

    • sean

      B.A.D lever would still be better for a right handed shooter its easier to manipulate then trying to use your trigger finger to use the ambi release.

  • hikerguy

    Something that just makes us southpaws want to jump and shout!

  • sean

    Is Falkor Defense the only company making a Charging handle that lock from the inside for this action?

  • Rio

    Anyone having issues with magazines not dropping free with these receivers?