Many of us tend to pick up a few empty brass cases while at the range. I myself tend to look for .308 empties that are reload able. Sometimes I get lucky and find a couple handfuls and some times I dont get any.
I bring the ones I find home and give them a good cleaning then a good inspection. Some of the things I find with differing types of brass are the rim may be thicker then most and the size of the flash hole can differ. Twice I have had stuck empties in my Howa and they both are CBC brass, which has a slightly thicker rim and the extractor has a hard time grabbing onto it. So these I save to use in my Cetme, which will fire anything and throw it out.
The flash holes I want all the same size so ignition is consistent. If I see the flash hole is smaller I will drill out the hole to the same size hole as a standard Winchester case.
Sometimes I also find some brass that the head is slightly tilts and if you stand the empty case up on its head the case tends to lean some, these I throw away, there has to be a reason they are like that and I am not going to take any chances.
Military surplus brass tend to be a tiny bit thicker then commercial brass so I tend to clean, resize them and trim the case mouth thickness so they will give a closer consistent performance as the commercial brass does.