Geissele Automatics 05314 Reaction Block Black Steel Armorer's Tool - AR-15/M4/M16

The Geissele Automatics 05314 Reaction Block is a professional-grade armorer's tool purpose-built for the assembly, maintenance, and gunsmithing of AR-15, M4, and M16 lower receivers. Machined from steel and finished in black, this reaction block provides the ultra-stable platform needed to perform a wide range of lower receiver operations with confidence.

Once the armorer has installed the buffer tube, the lower receiver indexes securely on the Reaction Block in one of three positions, giving easy and precise access to the trigger, magazine catch, and other internal components at both the 6 and 9 o'clock positions. This makes installing trigger groups, springs, detents, and pins dramatically easier compared to free-handing a stripped lower.

Designed and built by Geissele Automatics to the same quality standard the company is known for across its triggers, rails, and small parts, the Reaction Block measures approximately 8.2 in long by 3.1 in tall, fits any standard AR-15/M4/M16 pattern lower receiver, and is an essential bench tool for armorers, gunsmiths, and home builders alike.