Correct. I'm no machinist. That was exactly the explanation I hoped for.
I couldn't think of any reason why the units would matter, and you have given me some. Thanks. :)
The go out an buy a small lathe and mill and start making stuff! ;-D
I found this to be a fun hobby, even if I make more scrap metal than ends up in the projects.
I will eventually make some firearms, including rifling the barrels ... but, I need to practice a whole lot more first.
Browse http://hobby-machinist.com/ if you want to see some talent. There is a fellow there who posted step-by-step pictures of his rifle build.