Moviegoers continued to shell out for “Teenage Mutant Ninja Turtles,” while Sylvester Stallone’s action ensemble “The Expendables 3” was easily out-gunned in its weekend debut. Paramount Pictures’ rebooted reptiles took in $28.4 million in the film’s second weekend, according to studio estimates Sunday. That far surpassed the limp $16.2 million earned by Stallone’s gang of aged but buff warriors. The paltry, fourth-place total for “The Expendables 3” is well below previous debuts in the Lionsgate franchise. The last two “Expendables” opened with $34.8 million (in August 2010) and $28.6 million (in August 2012). The third film was the first to be rated PG-13 in the previously R-rated series, which potentially signaled watered-down explosiveness to an audience that was largely over 25, anyway.