Disney-Marvel’s “Avengers: Age of Ultron” is heading for a second weekend in the $75 million to $80 million range in the U.S., lifting the tentpole well past $300 million in just 10 days.

The opening of Warner Bros. and MGM’s comedy “Hot Pursuit,” starring Reese Witherspoon and Sofia Vergara, has been cooler than expected, with a launch in the $12 million-$13 million area after it drew $4.2 million on Friday.

Early Friday estimates saw “Ultron” climbing as high as $90 million, but those appear to have been overly optimistic. It grossed $21.3 million Friday in the U.S., slightly below earlier estimates in the $22 million-$25 million range.

The first “Avengers” movie set a record with $103 million in its stratospheric second weekend in 2012, declining 50% from its $207.4 million launch. “Ultron” now appears headed for a decline of about 58% from its opening — which could make it the second-largest U.S weekend ever if it finishes ahead of the $75.6 million taken in by “Avatar” in 2009.

“Avengers” went on to gross $623 million in the U.S. in 2012. “Ultron” should be at around half that total — $310 million to $315 million — by the end of the weekend.

On the international front, “Ultron” crossed the $500 million mark on Friday. That milestone has been surpassed by only 2012’s “Avengers” with $895 million and 2013’s “Iron Man 3″ with $806 million; with China opening on May 12, it still has plenty of box office mileage in coming weeks.

“Hot Pursuit” had been forecast to come in around $18 million as a counterprogrammer to “Ultron.” But the buddy comedy — which carries a $35 million pricetag — has been hammered by critics and appears to be falling short with audiences, notching a C-plus Cinemascore.

“Ultron” will face formidable competition next weekend with the openings of Universal’s “Pitch Perfect 2” and Warner’s “Mad Max: Fury Road” in the U.S. Early tracking suggests both will top $40 million in their launch frames.