I am familiar with the term when applied to firearms. I really do not care how my ammo looks as long as it goes bang. Is this something to be considered? I am confused as to the term itself.

Are you referring to something specific?

If a vendor is selling “blemished” ammunition, it’s probably not unsafe to fire or unusable because the cases are bulged or dented so badly that it won’t chamber. I would expect minor dents (that I’ve never found to be any sort of problem) or discoloration due to tarnish, etc. I wouldn’t want something that was corroded green, but discoloration is fine as well.

And of course the type of ammunition makes a difference as well. If I were purchasing something for precision rifle use I’d be more finicky than if it’s intended for range blasting.

I had to return a case of 357 sig to the manufacturer because the cases had black spots and what looked like rust. CCI paid for return shipping and sent me out a fresh case. It took over a month for the exchange but I wasn’t in much of a rush. I believe most ammunition is warrantied for a year after you purchase it.

I bought a few boxes of Federal .380FMJ that had what appeared to be tarnished water spots all over the brass cases. It wasn’t sold as blemished, but it should have been, IMO. Rather than make a long drive to complain about it, I just used it. It worked fine.