Survivors of gun violence and gun control advocates plan to deliver around 2.5 million postcards to elected officials across the country next week to demand political action on the issue.

More than 625,000 people signed on to support the postcard campaign, initiated by the pro-gun control groups Moms Demand Action for Gun Sense in America and Everytown for Gun Safety in the days following the May 23 shooting near the University of California Santa Barbara.

Beginning Monday, the organizations plan to hand-deliver a postcard to each supporter’s U.S. House representative, two U.S. senators and governor – about 2.5 million postcards in all. The campaign will run throughout the week.

The postcards were inspired by Richard Martinez, the father of one of the six victims in the Santa Barbara attack, according to the gun control groups. The postcards will call for “not one more” shooting death. Martinez – whose impassioned plea made national headlines in the wake of the shooting – will personally deliver postcards to the local offices of politicians in Tennessee, Florida, Pennsylvania and Iowa.

The postcard delivery plans come amid several recent wins for gun control advocates. A federal court in Colorado upheld the state’s gun law as constitutional Thursday, which requires background checks on some private firearms sales and limits ammunition magazines to 15 rounds.

The Colorado law is similar to a bipartisan bill that failed in the U.S. Senate last year. The federal background checks system doesn’t require unlicensed private sellers to perform reviews on potential buyers, nor does it request records of the sales be maintained.

The U.S. House of Representatives approved a bipartisan amendment in May to boost funding for background checks. The Senate will likely consider its own version of the measure before conferencing with the House to produce a final piece of legislation later this year.

“There can be no question that the universal background checks are fully compatible with the Second Amendment,” Jonathan Lowy, director of the Legal Action Project at the Brady Campaign to Prevent Gun Violence, said in a statement on Friday. “The Second Amendment is no excuse for congressional inaction.”

High-capacity magazines are banned in eight states and the District of Columbia. Magazines that can hold more than 10 rounds of ammunition are generally considered “large capacity”; some magazines can hold up to 100 rounds.

Large-capacity magazines are used in half of mass shootings in the United States, according to a review by Mother Jones that analyzed 62 such incidents over a 30-year span. The accused gunman in the July 2012 shooting massacre at an Aurora, Colo., movie theater used a 100-round magazine during the shooting, which left 12 people dead and scores wounded. Close video SCOTUS upholds law on 'straw buyer' purchases NBC’s Pete Williams reports on the ruling about ‘straw buyer’ gun purchases. share tweet email Embed

Chicago’s Democratic Mayor Rahm Emanuel recently recommended rules that would impose zoning limits on gun shops in the Windy City and require every gun sale be videotaped. Although the Chicago City Council unanimously agreed to allow for the establishment of such stores earlier last week, council members barred managers from opening them in most neighborhoods. Following Emanuel’s proposals, each shop must record all firearms sales.

The U.S. Supreme Court ruled on June 16 that it is a federal crime for someone to buy a gun for someone else in a so-called “straw purchase.” The law, according to the justices, helps keep weapons away from people who aren’t legally allowed to possess firearms, including individuals with felony convictions or mental illnesses.

But some pro-gun legislation, including the sweeping “guns everywhere” bill that was signed into law earlier this year by Georgia’s Republican Gov. Nathan Deal, has advanced in recent months. Additionally, a bill in Kansas will bar local government from enforcing community gun ordinances and make firearms laws uniform across the state.