The National Rifle Association's Political Victory Fund raised US$2.4 million ($3.3m) in donations in March.
It sets a 21st-century fundraising record for the group in the month after a gunman killed 17 students and educators at a high school in Parkland, Florida.
The unprecedented fundraising haul came as gun control advocates, led by student survivors of the shooting, saw legislative victories in a number of states and marched on the US Capitol to demand change at the federal level.
The data from the Federal Election Commission shows that US$1.9m of the US$2.4m total, about 80 per cent of it, came from small donations of US$200 or less, in line with the small-dollar share of previous months' fundraising totals.
A Chicago Tribune investigation found that the NRA aggressively stepped up its digital advertising in the wake of the Parkland shooting after survivors made opposition to the gun rights group a centerpiece of their advocacy.