I understand that this is totally anecdotal, but i have a factory FN SPR a3g (.308) that I've put over 2,000rds through. It's a super heavy rifle that a child can shoot .5 MOA @ 100yds all day long off a bench. After 100 or so rounds, it starts to open up to about 1.5 MOA. Once it's been thoroughly cleaned, it groups around 4 MOA for the first 7-8 shots, every single time it's cleaned. Like a light switch, on round 8 or 9, it goes back to the bullseye and is back to it's normal .5 MOA. It's been doing it for years, it happens so consistently I bring my cleaning kit to the range and do it in front of friends/shooters that have doubts. Hell, I even let them take the shots themselves to watch it happen.
I also have a few customs that love shooting clean, cold bore... so I'm definitely not saying it's one way or the other. I just assumed that every gun had it's own way. Am I wrong, is there something wrong with my FN? I'd love to hear suggestions on why it acts this way.