CA-Legal AR-15 Stock Adapter

Wrap your Hand around a Hammerhead

Please click the photo above to purchase.

Hammerhead™ replaces the pistol grip on your AR-15. When configured properly it can help you keep your rifle legal in jurisdictions where the pistol grip is restricted. In operation it feels very much like holding a wooden rifle. Manufactured from a very strong engineered polymer material, it'll survive the most challenging missions.  Hammerhead™ carries a five year warranty against defects in materials and manufacturing.

Popular CA-Legal configuration (Compliance note: mag permanently blocked to 10 rounds, and original telescoping stock is pinned to a fixed length)

Example NY-SAFE sporting rifle configuration with Hammerhead™ stock adapter,  RRA Entry Stock Kit, Entry Length Receiver Extension Tube, KNS Rear Takedown Pin and 5" Rubber Cover.

More Information


  • Mass: 170g without hardware
  • Overall Dimensions: 130x70x36mm
  • Tensile Strength: >197MPa
  • Flexural Modulus: >9.7GPa
  • Material: 33% Glass Filled Nylon
  • Max operating/storage temperature: 245C

(Specifications are subject to change without notice.)

Hammerhead™ is engineered and tested to work with mil-spec forged AR-15 lower receivers. While the product may work with billet lowers, these lowers often have wide variances in dimensioning that could impact the fit of this product. It may be necessary to modify the product to fit on any given billet lower.  Modifications to the product void the warranty.

CALIFORNIA: California Department of Justice Bureau of Firearms attests that Hammerhead™ is not a pistol grip and therefore legal when used on a detachable magazine semiautomatic centerfire rifle with none of the features listed in CA PC 30515(a)(1)(A-F).1

NEW YORK STATE: We have confirmed with Counsel for the New York State Police (NYSP) via our attorney (Tresmond Law of Hamburg NY) that a rifle with our Hammerhead™ AR-15 Stock Adapter when epoxied to the rifle and with a buttstock attached to the rear threads of this product (Type I or Type II config) and no other NY-SAFE prohibited features would be considered a sporting rifle and no registration under NY-SAFE will be required.

We make no claim concerning the legality of this product for use in complying with the restrictive firearms laws of any other state.

This product is licensed under U.S. Patent No. 6,374,528

1. Sworn testimony of Frank Navarro, CA DOJ Bureau of Firearms Special Agent, in the case of People vs. Haack and Haack, California County of Tulare Superior Court, 3 November 2010.