I've seen a fair number of posts arriving to the front page with ~5 points. One element could be the timing - if 5 points appear in the first, say, 15 minutes,

I've seen a fair number of posts arriving to the front page with ~5 points. One element could be the timing - if 5 points appear in the first, say, 15 minutes, it might be enough to raise it to the front page? Maybe there's an element of randomness, too. Dunno. I suppose HN algorithms are secret for a reason - if they were revealed, they could be optimized for.