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We're huge fans of the Big Green Reaction Block that ensures the buffer tube is properly aligned with the lower receiver, but the HK 416/MR556 parts don't fit. So, we developed this. It also acts as an alignment check tool.
We also developed a version for the TDP M4 buffer tube in the event the big green one is out of stock.
Choose which version you need in the drop-down list.
These are intended to be used with the Forward Controls Design JCW Joint Castle Nut Wrench available HERE. The built-in extension surrounds the buffer tube and precludes the need for a spacer to act against the wrench when applying torque.
Made from very serious carbon fiber reinforced high temperature nylon.
We also make a Roto-Reaction Block for TDP and HK 416 buffer tubes that allows 360° castle nut staking capability. Click HERE to see it.