So I was reading an old archived thread about Melonite vs NiB vs Ionbonding. There was a user saying that with the melonite barrels if you torque the extension on and then melonite it that barrel extension would come off after a few hundred rounds. So it has to be melonited then drill gas port and torque the barrel extension so basically if done right the gas port can never be melonited.

They also commented that Melonite has to be done before or in place of (wasnt sure which was meant) heat treating.

My question is are Bolt carrier groups normally heat treated? Can something be heat treated after melonite or does melonite do that during the process. Does QPQ Melonite solve some of these issues?

I have a barrel and gas tube that is melonite by a very reputable manufacture so I am sure whatever they did it was done right, but I bought a BCG that is melonite finish from someone who I havent heard of but seems reputable and was just wondering how the process works and if the metal stands up as well as a NiB or standard phosphate.

Never mind I think I finally found the info I wanted. Apparently the melonite QPQ process case hardens whatever your doing. Also there's a difference between Q, QP, and QPQ. Learn something every day.

Could you explain the differences? I would like to know. Or just list the places to look and who does the coating work.

Melonite - Ferritic nitrocarburizing is a range of case hardening processes that diffuse nitrogen and carbon into ferrous metals at sub-critical temperatures.

NiB - Alkaline Electroless Nickel Boron (NiB) is an autocatalytic coating process. The coating is deposited from an aqueous solution which contains either an alkylamineborane or sodium borohydride as a reducing agent, a source of nickel Ions, a buffer, complexant, and control chemicals. Nickel Boron coatings are columnar in growth resulting in a distinct nodular topography which serves to reduce surface to surface contact of two mating / sliding surfaces reducing drag / friction. The nodular structure dissipates heat at greater efficiency due to greater surface area.