Quick Tip: How To Use the Geissele Reaction Block
This guide details the use of the Geissele Reaction Block, a tool designed for AR-15 receiver extensions. Made from billet aluminum with polymer set screws, it securely holds mil-spec receiver extensions in a vise. The block's versatility allows for vertical, horizontal, or inverted orientations, simplifying tasks like magazine catch installation, grip installation, and thread cleaning.












