STS416 A5 Lower Receiver

Precision-Built HK 416 Style Lower

The STS416 A5 Lower is a billet-machined receiver engineered to replicate the original HK MR556, MR223, and BRN-4 lowers with extreme accuracy. Over six months of laser scanning, CMM inspection, and CAD refinement ensure a perfect match to HK’s forged specifications—down to critical alignment features with the upper.

Why Billet? Why It Takes Time

HK 416 forgings are no longer available, so we’ve created the next best thing—a billet 7075 T6511 alternative. Because billet receivers start from solid stock, the machining and deburring process is significantly more complex than working with forgings. Achieving authentic contours, textures, and symmetry requires advanced setups and precise craftsmanship.

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 compliance reasons. For engraving services, 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 yours.
Please have your FFL dealer email a signed copy of their license in PDF format to:

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

Need a Matching Upper?

We recommend pairing this lower with the HK416A5 Upper from HKParts:

🔗 Buy from HKParts.net

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