Berchwood Casey makes and sells a liquid preparation that chemically blackens aluminum, called Aluminum Black. See if your local gunshop has some.

If you can't get it locally, Brownells sells it. Brownells also sells their own aluminum-blacking stuff, Aluma-Hyde, a spray-on lacquer. You have to first use a primer, which they sell too.

So have you used the the birchwood casey aluminum black before? Anybody have reviews on this stuff or pictures of before and after?

I have never used Aluminum Black.
However, I have used other Birchwood Casey chemical preparations, and they do a good job.
I suggest that you probably will not do any irreparable harm using Aluminum Black, so I suggest that it's worth a try.

Brownells' Aluma-Hyde lacquer will be just as subject to wear as the Aluminum Black will be, but I believe that the lacquer will be harder to touch-up when it wears off.

"Yer pays yer money and yer makes yer choice."

ok thank you