Harry Potter and the Half-Blood Prince made $17.9 million in its third weekend in theaters — beating G-Force, the movie that topped Harry the previous weekend.  In addition, Half-Blood Prince was down only 39% from last weekend.  That’s a smaller-than-normal drop, which Movie Cultists notes is thanks to the film showing up on hundreds of IMAX theaters across the country.

Half-Blood Prince finished the weekend with a new $255.7 million total domestic haul.  Since then, it’s been making a steady $2-2.5 million per day, and on Wednesday surpassed the gross of 2002’s Harry Potter and the Chamber of Secrets.

It should beat the $292 of Harry Potter and the Order of the Phoenix to become the second-highest grossing Potter film after Sorcerer’s Stone (which made $317).  But will it surpass the $300 million mark?