Hillary Clinton repeatedly has said she’s not here “to take your guns away,” but her campaign platform would go a long way toward stopping Americans from being able to buy some of the most popular firearms on the market.

The former first lady is walking a fine line on guns as she tries to peel away independents and some Republicans from Donald Trump while also painting herself as a gun control champion. On the campaign trail Mrs. Clinton frequently calls for new gun safety measures as she reassures law-abiding Americans their firearms won’t be targeted under her would-be administration.

On several fronts, however, it’s clear a Clinton administration would result in much tougher gun laws, including some that would affect Americans with no criminal records. And critics such as Mr. Trump and powerful gun rights groups fear Mrs. Clinton would reshape the Supreme Court by appointing justices much more hostile to Second Amendment freedoms.

While many Democrats long have been labeled as anti-gun, firearms advocates say Mrs. Clinton’s position is especially disingenuous.

“This is an outright and outrageous lie that [Mrs. Clinton] doesn’t want to take people’s guns,” said Dudley Brown, president of the National Association for Gun Rights. “Hillary Clinton has made a career of restricting citizens’ Second Amendment rights and trying to ban, outright ban, entire classes of firearms. And if that’s not taking guns then I don’t know what is. All you have to do is pay a little bit of attention.”

Mrs. Clinton’s platform calls for an expansion of background checks for all firearms purchases. She’s also called for a reinstatement of the national assault weapons ban and a prohibition on high-capacity magazines.

The former secretary of state also is a staunch supporter of the so-called “no fly, no buy” proposal that would stop anyone on federal terrorist watch lists from buying guns. The plan has been rejected by civil liberties advocates who say such a ban — which would apply to Americans who haven’t been charged with a crime but merely are on the government’s radar — is a blatant violation of due process rights.

While running for U.S. Senate in 2000, Mrs. Clinton also supported legislation that would’ve established a national federal registry for all guns — though such an idea doesn’t appear to be part of her 2016 presidential platform.

The Clinton campaign did not respond to a request for comment.

In addition, Mrs. Clinton has supported raising the legal age for all handgun ownership to 21. Current law allows anyone over the age of 18 to own a handgun, though licensed dealers can only sell to those over 21 years of age.

In an attempt to keep blue-collar, rural Americans on his side, Mr. Trump has made Mrs. Clinton’s gun control agenda a centerpiece of his own campaign and is fomenting fear among firearms owners.

“I believe if my opponent should win this race we will have a Second Amendment which will be a very, very small replica of what it is right now,” the billionaire businessman said at last week’s presidential debate in Las Vegas. “But I feel that it’s absolutely important that we uphold [the Second Amendment], because of the fact that it is under such trauma.

The National Rifle Association already has spent millions of dollars on political ads attacking Mrs. Clinton’s position on guns. In one ad, a woman’s home is broken into, and her firearm disappears as she opens her gun safe.

“Don’t let Hillary leave you protected with nothing but a phone,” the ad says.

For her part, Mrs. Clinton stresses that she’s well acquainted with the cultural importance of guns and has pointed to her own history in rural America.

“I lived in Arkansas for 18 wonderful years. I represented upstate New York. I understand and respect the tradition of gun ownership. It goes back to the founding of our country,” she said at last week’s debate. “But I also believe that there can be and must be reasonable regulation. Because I support the Second Amendment doesn’t mean that I want people who shouldn’t have guns to be able to threaten you, kill you or members of your family.”

Indeed, Mrs. Clinton and her running mate, Virginia Sen. Tim Kaine, have received the endorsements of powerful gun control groups, some of which have said the Clinton-Kaine ticket is a historically strong gun control combination.

“She has made our safety the centerpiece of her campaign,” Dan Gross, president of the Brady Campaign to Prevent Gun Violence, said earlier this year, referring to Mrs. Clinton.