Now I have been wrong a time or two before , I alwyas thought the coating was not environmentally friendly so it was not done in the US.
?????
Tenifer and Melonite are simply trade names for a process - referred to as Ferritic Nitrocarburizing - that accomplishes the same thing (surface hardening) using different chemicals. The Tenifer solutions aren't allowed in the U.S. while the Melonite process is approved. I suspect this fact had absolutely nothing to do with the decision to produce, or not produce, certain pistols or components in the States.
The uninitiated are always easily impressed. NRA Endowment Member
, I alwyas thought the coating was not environmentally friendly 
so it was not done in the US. 
