I'm a fig fan of Norrell's Moly Resin.really easy to use. you pre-heat the part @ 100 degrees apply it with an air brush. The pre-heating eliminates runs as the moly resin dries on contact. Then you bake it in the oven @ 300 degrees for an hour. Some tough stuff for sure! Have used it on many rifles. I like the U.S. SOCOM flat black best as it is the closest to the AR-15 finishes I have found. I have also used the semi gloss black and it matches the HK type finishes very well. Moly resin is suppose to be more durable than Duracoat but I have never used it. Here is a link to the product: http://www.molyresin.com/
BTW: I still have a 3/4 bottle of the semi gloss black if someone wants it. Should be enough to do at least two rifles.