The NRA has also launched a campaign to add 100,000 new members in 100 days, saying "the threat to our Second Amendment has never been greater."
While the organisation doesn't make membership data public, it currently claims about five million members.
The NRA's Political Victory Fund is a political action committee that issues the group's influential legislative scorecards and spends money on behalf of candidates and campaigns during elections.
But it represents just a small part of the NRA's total lobbying, fundraising and political spending efforts. In 2016, for instance, the Political Victory Fund raised more than US$11 million but the NRA overall spent tens of millions of dollars on federal and state-level elections. Much of that spending came from the NRA's Institute for Legislative Action, its lobbying shop.
The surge in donations last month suggests many gun rights supporters are concerned about a change in the national gun policy landscape following the Parkland shooting.
Gun control activists have won the passage of significant new restrictions on gun ownership in Republican-led states such as Florida and Vermont. And a federal expansion of concealed carry privileges that passed the House late last year is currently facing uncertain odds in the Senate.
All of this is taking place against the backdrop of the 2018 congressional elections, as both the Parkland survivors and NRA hope to elect lawmakers who share their positions.