Under what conditions is a football helmet most likely to be knocked off? I realize it helps if the chinstrap isn''t buckled, but where would the hit come from?

The straps connect on either side of the helmet. I would think a hit from either side could disconnect one fastener, and the weight of the helmet would force the fastener on the other side to let go.

considering I've done it and I've seen it done to my teammates, it happens usually when you get under the player's facemask and then rise up through the hit. If you come hard enough it will pop right off, usually when the person being hit isn't paying as much attention to the hit (i.e. going for a pass over the middle) your chinstrap can be buckled and it will come off if you hit them just in the right place at the right speed.

if u put it on and u shake ur head and it moves a lot u should get a smaller one, getting used to ur helmet takes like a week, the first time i got mine it was tight as hell but it put pressure on my head but then i gto used t oit

A hit to the earhole or chin would do it.

if you hit soft maybe but if you dont hit like a nut HELL NO