President Joe Biden cited 9 mm guns in a new address about gun control.

The comments on Memorial Day come one day after Biden visited Uvalde, Texas, to meet with the families of victims and survivors of a school mass shooting that has prompted a wave of advocacy for more restrictive gun control regulations.

Speaking with reporters on the South Lawn of the White House, Biden had been asked how close Congress may be to settling on gun access reforms, including red flag rules, to which he said it is "hard to say" because he has not been directly bargaining with Republicans.

He spoke about a trauma doctor from New York who, decades ago, while Biden was a senator and holding hearings on what "rational" gun laws could be, showed him an X-ray while talking about "probably" being able to remove a 22-caliber bullet lodged in someone's lung to save a life. “A 9 mm bullet blows the lung out of the body," Biden added. "So the idea of these high-caliber weapons — there’s simply no rational basis for it in terms of self-protection, hunting."

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In fact, 9 mm handguns are prevalent for self-defense and concealed carry.

Sen. Chris Murphy (D-CT) told ABC on Sunday that Congress is holding "serious" bipartisan negotiations on legislation meant to impede gun violence. Biden did note that he believes "things have gotten so bad that everybody is getting more rational about it.”

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"We're talking about red flag laws. We're talking about strengthening and expanding the background check system, if not universal background checks. We're talking about safe storage. And yes, we're also talking about mental health resources and more security dollars for schools. A package that really, in the end, could have a significant downward pressure on gun violence in this country," Murphy told ABC News's Jonathan Karl. "Maybe that's the most important thing we could do is just show that progress is possible and that the sky doesn't fall for Republicans if they support some of these common sense measures."

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Twenty-one people, including 19 children and two teachers, died in the shooting in Uvalde on Tuesday. Law enforcement killed the gunman, identified as an 18-year-old who officials say legally purchased two AR-15-style rifles and hundreds of rounds of ammunition.

“There’s only one reason for something that can fire 100 shots," Biden said.

The President also said the Second Amendment "was never absolute." He added, "You couldn’t buy a cannon when the Second Amendment was passed," a claim he has made before that fact-checkers have examined and deemed false.