Bushmaster says that they put a milspec "Manganese Phosphate" Finish on their barrels.  
Isn't that the same as parkerizing?

Anyone?

There are two types of parkerizing.  One is Zinc Phoshate which has a grey color and the other is Manganese Phosphate which is closer to black.  Bushmaster also uses a Nickle Acetate final seal.

So all Manganese Phospate is parkerizing but not all parkerizing is Manganese Phosphate.  Also not all Manganese Phosphate finishes are the same as the Bushmaster finish with the Nickle Acetate seal.  I hope this helps.

There are 2 types of "Parkerizing."  

Manganese Phosphate (The good stuff) and Zinc Phosphate (I think).