Milwaukee, Wisconsin - Donald Trump's running mate J.D. Vance delved into his personal history for his big speech at the Republican convention Wednesday – and no family member earned a bigger cheer than his gun-totin' grandma.

Vance, who famously chronicled his difficult upbringing in best-selling memoir Hillbilly Elegy, reflected on how his Ohio hometown had been blighted by closed factories and addiction.

"I had a guardian angel by my side. She was an old woman who could barely walk, but she was tough as nails," he told the Republican National Convention in Milwaukee, Wisconsin.

"I called her mamaw, the name we hillbillies gave to our grandmothers," said the 39-year-old Ohio senator and newly confirmed vice-presidential candidate.

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Vance went on to describe how his grandmother had died in 2005, shortly before he left home to serve in the Iraq war.

"When we went through her things we found 19 loaded handguns," explained Vance, drawing raucous cheers of "Mamaw, mamaw" from the partisan crowd.

"They were stashed all over her house – under her bed, in her closet, in the silverware drawer... this frail old woman made sure that no matter where she was, she was within arm's length of whatever she needed to protect her family."

"That's who we fight for. That's American spirit," he said.

Vance's remarks came days after Trump, the former president and Republican nominee for November's election, survived being shot in an assassination attempt.

Trump was wounded in the ear and a rally attendee was killed on Saturday in Butler, Pennsylvania. The gunman was shot dead by Secret Service snipers.

President Joe Biden has called for a ban on the type of semi-automatic rifle used in the attempted assassination.

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In his speech, Vance also paid tribute to his mother, a former addict who had been sober for almost a decade.

Vance suggested the family celebrate the anniversary in the White House in January, "if President Trump's okay with it."

It earned a nod from his boss, who was watching on from the VIP box ahead of his own big speech, scheduled for Thursday.