This, without question. This will get you durability and protection.
FIFY
Printable View
Yep, np3 looks great
https://www.m4carbine.net/showthread...R-RANGE-REPORT
Cerakote
A good friend of mine does Nickle Boron Nitride plating. Here's a pic of a Seekins upper and lower set he did:
http://i197.photobucket.com/albums/a...ps89331879.png
If it's something you'd be interested in, shoot me a PM and I'll get you in touch.
Pewter Cerakote is my recommendation