I use to use seconds and blemished bullets to save the "good" bullets, But now I like to chronograph a barrel as I am breaking it in to see the changes as the break in proceeds and tel me when it is broken In. And often it also tells me if the barrel likes a certain bullet or not, So I now start with a middle pressure load with the powder and bullet I would like to use, and actually end up shooting far less rounds before I find the best load.
Doing it this way, it is like a three in one method. Break in, velocity check and component check at the same time.
If you don't have a chronograph, you can use any bullet you have and end up with a good break in and go from there.
Just the way I like to do break in.
J E CUSTOM