Coated lead bullets are pretty new
The gas check was a way to deal with the isuse Uncleinick mentioned (that is new to me as well but gas check stopped lead issues, did not know what the mechanism is, good info but as often is true, if you avoid it consistently that is what counts!
I have 9mm lead bullets that have 3 grease groves.
This is an interesting read. I do have some of their bullets and no issues in 9mm. The grease does smoke some, I think coated are probably better but no experience.
http://www.pennbullets.com/unique.html
http://www.pennbullets.com/Reloading...oadingTips.htm
Keep in mind, hard is just one aspect of a metal, there are all sorts of added elements as well ash how the metal is processed that end in various characteristics.