Echoing recent recommendations from the White House, Biden called for universal background checks for gun buyers; expansion of mental-health facilities; a crackdown on so-called straw buyers; and a requirement to report lost or stolen guns within 24 hours.
The 90-minute session at Girard College in North Philadelphia included a who's who of Pennsylvania Democrats - Mayor Nutter; District Attorney Seth Williams; State Sen. Bob Casey; U.S. Reps. Bob Brady, Allyson Y. Schwartz, and Chaka Fattah; state Attorney General Kathleen Kane - as well as Philadelphia Police Commissioner Charles H. Ramsay, Wilmington Police Chief Christine Dunning, and other police officials.
Several times, Dunning left to get updates about the Wilmington shooting.
Biden plans to host a series of discussions around the country to promote stricter gun laws. Critics have accused him of choosing sympathetic venues such as Philadelphia, where he was surrounded by fellow Democrats.
"They say, 'He won't go to Cambria County. He won't go to Luzerne County,' " the vice president said. "But I'm coming. I'm coming. We cannot wait."
His visit came a day before the State of the Union address, in which President Obama is expected to pitch new gun limits.
Two recent polls have found increasing support in Pennsylvania for some of the measures Obama and Biden are pushing. In the latest, a survey of 485 registered voters released Monday by Mercyhurst University in Erie, a majority said banning military-style assault weapons would help prevent mass shootings, and a ban on large-capacity magazines would help.
Biden pounded those themes, saying "the greatest concern of big-city chiefs" was semiautomatic weapons with "high-capacity magazines and large-caliber bullets."
He lamented the 2011 layoffs that "cut the Camden police department in half" (the number was nearly half the force; some of those officers have since been rehired) and said he is pushing for a federal commitment to spend $4 billion "to put another 15,000 sworn officers back" on the nation's streets.
Nutter said that "the No. 1 issue" for cities like his is eliminating illegal handguns with high-capacity magazines. He also called for updating national crime databases with names of 600,000 people who "should not be able to purchase a weapon" because of problems in their backgrounds.
Like Biden, Nutter has compared Newtown's toll to the nation's, saying, "There's a 'Newtown' in America every day - 33 people are murdered . . .."
Casey, who in the aftermath of Newtown switched his stance and said he would vote to ban assault weapons, called Monday for full funding for a federal program to buy bulletproof vests for local police departments.
And a congressman, Brady, bragged of the grades he gets from a group sure to push back against the White House proposals - the National Rifle Association. "Zero F-minus," he beamed, drawing a chuckle.
Turning serious, he recalled seeing then-U.S. Rep. Gabrielle Giffords on Capitol Hill the Friday before she was gravely wounded in her Arizona district.
"I said, 'I'll see you on Monday,' " Brady said. "But I saw her [on TV] Saturday, on a gurney being rushed to a hospital."
Biden said nothing he and Obama are proposing would impinge on the Second Amendment's guarantee of every American's right to "responsible" gun ownership.
Nor, he said, should anyone worry that Big Brother-style restrictions are on the way.
"There is that old saw that this is a slippery slope," he said. Unabated gun violence is "the slippery slope I am worried about."
Contact Michael Matza at 215-854-2541, firstname.lastname@example.org, or follow on Twitter at @MichaelMatza1.