I do believe the term'break-in' is over used in forums, unless the manufacturer states it in their users manual. Even then the cost of ammo being what it is the manufacturer should break it in before you buy it, or give you free ammo to break it in yourself.
I'm glad I didn't have to break in a newely issued firearm when I went to Nam'.
I can see it all now. Don't shoot me. I'm just going thru my break in period or taking a non functioning weapon into the armorer and him saying don't worry it is going thru it's break in period. Just keep your head down for the next 200rds. If it doesn't work after that bring it in and I'll see if I can get it back to you in the month or two.