MPN: 05-314


  • Faster and easier AR lower receiver assembly or disassembly
  • Lower can be attach at different angles (12, 3, 6, 9 o'clock) for better access to parts


  • Material: Steel
  • Finish: Black


  • Any firearm with Mil-Spec buffer tube


  • 1x Geissele Reaction Block
  • 3x Retaining Screws


If you’ve ever wished for an extra hand during a rifle build you’re not alone. Sometimes it just doesn’t work to set down a partially built receiver so you can get a fresh angle of attack during assembly. How many times have you discovered you need something that’s just out of reach while you’re trying to marry parts?

Geissele Reaction Block Will Make Building Your Next AR-15 Much Easier

Geissele Automatic has an answer to the need for extra hands during the assembly of your next AR-15 build. The Geissele Reaction Block for AR-15 is designed to hold the Mil-Spec buffer tube during assembly of the lower receiver. When you use a Reaction Block, your hands are free to do the real work of an armorer, rather than the frustrating juggling act we’ve become accustomed to.

To use the Geissele Reaction Block for the assembly of your AR-15, or AR-10 build, just mount it firmly in a standard bench vise. It’s ready to hold your lower receiver as soon as you’ve installed your Mil-Spec buffer tube.

How Does The Geissele Reaction Block Works?

To begin, simply slide the buffer tube into the Reaction Block in your desired position and tighten its nylon screws holding your piece in place. As you work you can rotate your lower receiver to 12, 3, 6, and 9 o’clock positions making it simple for you to complete the build with minimal frustration. You’ll have the use of both hands and full access to the piece you’re working on. You may even finish that build in record time.

Geissele Automatics' staff of Pennsylvania craftsmen are shooters and armorers. Their motto is all you need to know: “We Manufacture Confidence.” Let them take the frustration of receiver juggling off your hands, assemble your next build with the confidence provided by the Geissele Reaction Block.

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