AS Designs ARC-Fire V2 HK416/MR556 Kit

This ARC-Fire V2 package is the HK416 and MR556-specific selector path sold by HK Parts. It includes ambidextrous selector levers made to work with the ARC mechanism and comes in 0-45-90, 0-45-180, and 0-90-180 configurations. HK Parts lists SKU HKP-22890-M at $249.95 and distinguishes it from the ordinary AR-15 ARC-Fire retail kit.

AS Designs' MR556 installation documentation covers MR556, MR223, HK416, and BRN-4 bolt carrier groups across the A1 and A4 generations without modifying the stock carrier. The fire control group still matters. AS Designs specifies an AR-15 mil-spec fire control group with its pre-cut trigger, or a Geissele MR556 trigger that has received the Super Safety clearance cut. The Geissele MR556 hammer is full size, so that path does not require the separate lever blocker.

HK Parts lists MR556 A4 and HK416 A5 as the straightforward current hosts, while its product page makes gas-system recommendations that vary by generation, barrel, ammunition, and suppressor use. Treat those settings as configuration-specific tuning, not as universal installation values. This exact kit is builder-locked to the catalog's MR556 A4 rifle and SBR platforms; the older MR556 A1 and select-fire HK416 families remain documented fitment but are not separate builder platforms here.