It appears Summit succeeded in getting the most warm bodies into plexes Friday with zombie-themed romcom “Warm Bodies.” The laffer drew $8.1 million Friday, keeping it on track for a $20 million weekend.Of Friday’s gross, $520,000 came from Thursday night previews. Much like Universal’s success with scarer “Mama,” “Warm Bodies’” PG-13 rating is likely working in its favor this frame as many new releases for the last two months have been R rated. “Mama,” in its third week in release, only dropped to fourth place with $2.3 million Friday. By comparison, “Texas Chainsaw 3D” — an R-rated scarer from January — dropped from first to ninth in its soph sesh. Warner Bros. bowed Sylvester Stallone actioner “Bullet to the Head” this frame with a $1.7 million haul for sixth place Friday. Pic’s looking at a modest $4.6 million take this weekend. At this point, it’s hard to say what effect, if any, the national conversation on gun violence in entertainment media — prompted by a devastating shooting on Dec. 14 in Newtown, CT and a resulting series of executive orders issued by President Obama on gun control — is having on the film’s gross. Similarly disappointing, Lionsgate opened “Stand Up Guys” on Friday to $528,000, putting it in the neighborhood of 15th place between “Argo” and “The Hobbit: An Unexpected Journey.” To be fair, and perhaps not to draw attention away from its subsidiary’s more promising and more aggressively promoted “Warm Bodies,” Lionsgate opened “Stand Up Guys” on a conservative 659 screens. “Stand Up Guys” is expected to take $1.5 million through Sunday. After “Warm Bodies,” last week’s winner “Hansel & Gretel: Witch Hunters” took around $2.9 million Friday for second, while Weinstein Co.’s “Silver Linings Playbook” earned $2.4 million for third.