Damn, I didn't know that about .5s. That's all I use, and they had to buy me separate lead last time (years ago) because every other loser here uses .7. It's the same with pens, I use the "micro" .5s and everyone else uses the fat ass "fine" .7s. I feel like I'm writing with a boat when I use one of theirs.
I've got the same set of mechanical pencils I used in college, over 30 years ago, at home somewhere. Obviously I rarely use them anymore if I don't know where they are, but I guess that is good because I'd probably get rustled trying to find lead.