Why are some bushmaster barrels coated like sandpaper?

[migkillertwo]

I've held a few bushmaster AR-15s and some of them have this coating on the barrels that feels like sandpaper. Does anyone know why they do that?

 

[Dionysusigma]

You mean the parkerizing?

 

[jakk280rem]

i know what he's talking about. a few months ago, i was in the market for an ar. some of the bushmasters i looked at seemed almost to have a traction coating on the barrel. very rough. i also noticed they were starting to rust already.

 

[ifit]

they are manganese phosphate finished to guard againts exterior rust or corrosion/non relflective finish.

 

[highorder]

It's thirsty parkerizing. It wants oil!

 

[Z-Michigan]

It's manganese phosphate parkerizing, but yes it seems coarser on Shrubmaster products than others. I suspect it's mostly a result of a coarser metal finish before the salt bath. FWIW, manganese phosphate is always somewhat coarse as inherent to the finish.

Boeshield T-9, another protectant, or any good oil will protect it from rust. Hi-temperature paint is also an option.