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Date Posted: October 19, 2011
AR-15 Parts: Are yours anodized correctly?
Shelley Sargent
Anodizing is a crucial, but often overlooked process for AR-15 components

In the pictures above, I've got pictures of two upper receivers... one with 5000 rounds through it, and one with 600. Turns out, the one with a big chunk of soft and bare aluminum showing is the less used receiver! This is because this receiver was from a relatively new AR parts manufacturer, and it was not hard coat anodized!
Hardcoat anodizing (also called hard coat anodizing, or hard anodizing) is a process that forms a very hard, dense, and relatively thick coating of aluminum oxide. This coating is particularly useful in applications requiring high wear resistance, in many cases outperforming hard chrome or electroless nickel. The coating material formed in this process occurs in nature as corundum, and is the second-hardest naturally occurring substance, second only to diamond. Hardcoat is often described as being "file hard", since it is difficult to scratch, even with a mill file.
After reading through a few armorer's manuals, and also being on hand with custom lowers/uppers being made, i've learned that one part of modern firearms construction that a lot of up and coming shops haven't mastered yet is anodizing.

If you were into AR-15s about or year or so back, it seemed like everyone and their cousin suddenly started producing uppers and lowers and releasing them for ridiculously low prices. Some products seemed a little iffy from the beginning, though a lot of the new offerings seemed like a good deal: Aluminum lowers and uppers at 25-50% off the prices we were used to.

Some of the new batch of "new name" uppers had off centered machining, some lowers has out of spec pistol grip scew locations, FCG holes... pretty obvious problems.

Less obvious was the anodizing, since it's an issue relating to the durability of the rifle. Turns out "Type III" anodizing or "Mil Spec" anodizing as advertised might not give you what you want. The type of anodizing used on government contract receivers is very specific... and it is why gov rifles that have been beat to crap and have their cosmetic finish nearly worn off from years of abuse... still don't have untreated bare aluminum showing.

Mil spec anodizing for rifles needs to penetrate into the the aluminum receiver and harden it. A lot of young gun brands "anodize" but their stuff is just like paint: it scratches off and it doesn't actually harden the aluminum. On my $75 lower, you can scratch off deep black and attractive finish on the edges and get straight to soft, bare aluminum! Whoops!
Ideally, you'd want a receiver that was mil spec, hard coat anodized... and optionally, teflon coated for cosmetic purposes. Some brands are incorrectly anodized and don't harden the aluminum, some brands are only teflon coated... these are the brands you want to avoid and are typically "young" companies which might have been contracted out to do just one part of the AR build process before deciding to strike out on their own.

So take heed: when buying receivers, sometimes it's worth it to go with established brands... I now know that the notion "a lower is just a lower" isn't true!




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