STS416 A1 Lower Receiver

Authentic HK 416A1-Style Lower

The STS416 A1 Lower is a precision billet-machined receiver replicating the design of the HK MR556, MR223, and BRN-4 lowers. Developed over six months using advanced laser scanning and CMM technology, this lower is dimensionally and aesthetically matched to original HK standards—ensuring excellent fitment and visual accuracy when paired with HK-style uppers.

Why Billet? Why It Takes Time

With original HK 416 forgings no longer available, this lower is cut from solid 7075 T6511 billet aluminum. Matching the forged HK aesthetic through billet machining requires an extremely complex machining and deburring process, especially in the receiver’s detailed exterior contours. Precision takes time—but the result is worth it.

Specs & Options

• Material: Billet 7075 T6511 Aluminum

• Finish Options:
  • Type III Hardcoat Anodized with Teflon
  • Proprietary Cerakote RAL8000 Blend

• Serial Numbers:
  • Standard format: 88-XXXXXX
  • Custom serials available (to match your HK upper serial, etc.)

⚠️ HK markings are not included for legal compliance. For engraving, we recommend: BlackOps Defense. (we can ship directly from us to them, contact BlackOps defense and provide STS with your BlackOps Defense order number to let them know what to do with your lower)

Shipping & FFL Instructions

This product must ship from our FFL to your FFL.
Please have your FFL dealer email a signed PDF copy of their license to:

📧 sales@specializedtactical.com
Subject Line: Your Name + Order #

If you are new the HK world and would like help understanding the various models, please visit our friends and this thread at: HKPro.net