I sort
ALL my rifle brass, especially .223. There's just too much variance between all the hundreds of different manuf.
For handgun, sometimes I sort. Range blasting ammo for 9mm is always mixed brass. I get the brass from a vendor @ Amazon, it's all cleaned and shiny,(I suspect it's ultrasonic cleaned), but there is at least 30 different headstamps in a 500 round small FLB.
If I'm doing a load work-up, that's a different story. I
will sort for an American headstamp, usually there's enough
WIN or R-P in a box for 100 cases. I stay away from FED, no real reason, just don't like it.
If I'm having a problem hitting something, I may sit down, run 5 or ten rounds at a clean target to verify the load is consistent. I then go through the box of ammo, picking the same headstamp from the mix. I just eliminated the variance of different headstamps, sort of instant match ammo!