Blackening Blackout Brass
by Kirk Lawson

I got a bug to try do something to differentiate my 300 AAC Blackout ammunition so that it was visibly distinct from 5.56 cartridges. I'm certainly not the first, and there have been many others before. The solution which eventually caught my fancy was to blacken the brass for the cartridges. There are several commercial manufacturers but most notable has been Noveske and Sig Sauer.

Rectangle Office supplies Font Publication Book

[Noveske 300 AAC Blackout]
Brown Cosmetics Rectangle Font Office supplies

[Sig Sauer 300 AAC Blackout]

After a lot of experimentation, I've come up with a process which yields similar results.

Wood Toy Machine Metal Electronic component

[Homebrew Black 300 AAC Blackout]

Wood Plant Font Natural material Office equipment

[Homebrew Black 300 AAC Blackout]

Office supplies Writing implement Writing instrument accessory Wood Office equipment

[Homebrew Black 300 AAC Blackout]

While Noveske, and presumably Sig Sauer also, uses a plating process, I used an oxidation process.

The first step is to use a Brass Black product. Of the ones I tried, the one which gave the best results at blackening the brass was Caswell Plating's Black & Brown Oxidizer.

Liquid Bottle Fluid Paint Plastic bottle

[Caswell Plating Black & Brown Oxidizer for blackening brass and copper]

The process is simple and effective, and Caswell told me that their process would not cause the brass to weaken or cause Stress Cracking as ammonia based cleaners can. They reported that some competitive shooters use their product to "mark" their brass to identify it for later collection.

After doing your complete case prep, including resizing, clean the brass well. You do not want any residue of the resizing lubricant on the case because it can prevent the solution from evenly blackening the brass.

Simply submerse the clean, dry, brass in the Caswell solution for a few minutes. It will become midnight black. Then remove from the solution, and rinse in cold water. The solution is good for several uses but will eventually become contaminated and lose effectiveness. It is a consumable.

After the brass is blackened, it will seem as if it is covered with a thin layer of charcoal. It will rub off and smudge onto your fingers. Even if you rub it off with a paper towel or cloth, it will still be dull and inconsistent, showing "scratching."

Line Material property Cylinder Tints and shades Pipe

[Blackened brass hand rubbed with a coarse cloth]

Frankly, I think it is ugly. When I got to this point, I had decided that I hated it and would just polish it back to bright brass.

This was where lightning struck and my luck kicked in. To clean brass, I have been using a rock tumbler with a squirt of Dawn dish detergent, a couple large pinches of Lemi Shine, and warm water, in with steel BB's. I have been using BB's instead of stainless steel pins. They're less expensive and are easily found in most sporting goods departments.

Liquid Drinkware Bottled water Solution Bottle

[Rock tumbler with BB's, Lemi Shine, Dawn, and warm water]

A 15 minute go-round in this and it comes out looking polished black and shiny. It has been described as almost black polished nickle with highlights of gold hinting through.

Tool Wood Walking shoe Outdoor shoe Metal

Tableware Toy Dishware Kitchen utensil Serveware

[Homebrew blackened 300 AAC Blackout brass]