Below is a picture of brass recently fired from my 308 Savage. The middle two pieces are Hornady match 308 168gr bthp. The outside are different manufacturers.



This is my first time cleaning brass so I don't know if this happened before. However, almost all the Hornady ammo shot yesterday had this blackend discoloration. the pic was taken after tumbling and hand wiping with a clean rag. A couple questions:
1. what causes this? I assume since almost exclusively inthe 50+ shots I took yesterday, all the Hornady brass shows this on the neck. The other brass (a Federal gold and some Lack City brass reloaded by Chad) did not show any of this.
2. Is this something that I should be concerned with?

You're good. Brass cases will often have some discolorations sometimes in them. You can try to tumble them longer and see if the black is from the carbon from firing them, or is part of the brass itself. It's kind of hard to tell in the picture.

It was hard for me to tell since I have no experience in such.

To my layman's eyes, it looks like brass discoloration and NOT carbon/crud on the surface of the brass neck. the pic is very crappy. It is only on the neck as well. And I assume since I wiped all the brass pretty thoroughly by hand with a clean rag, I assume anything left was not powder residue.
I ask because I really was counting on using this Hornady factory brass.

Looks like staining/soot around the case necks. I get it all the time with my 270. Tumble longer, washing them gets it off most times for me.

Wouldn't concern me in the least but I would wanna know what it really is.