Piston driven AR-15s have used bolt carrier with integral gas keys for years. Now, Voodoo Innovations, a sister company of Adams Arms, is bringing carriers with integral gas keys to direct impingement AR-15s. Loose gas keys may soon be a thing of the past.
Voodoo Innovations states that these bolt carrier groups are built to the MIL TDP (except, obviously, for the gas key specs) and then given their LifeCoat treatment. LifeCoat is a trade name that Voodoo Innovations uses for a variety of different coatings and treatments depending on the application. In this case, they are claiming that the coating will add durability, lubricity, corrosion resistance, and carbon resistance to the bolt carrier group.