Brown's show was criticised by senior police officers
Illusionist Derren Brown's Russian roulette stunt on Channel 4 drew 2.9 million viewers, according to unofficial overnight ratings.
This was about half the amount who watched the Agatha Christie mystery Sparkling Cyanide on ITV1 (6.1 million).
Both were beaten by BBC One's Waking The Dead, which drew 7.1 million.
Meanwhile, about 12.5 million earlier tuned in to watch Coronation Street's first gay kiss, according to ratings.
They saw Todd Grimshaw, played by Bruno Langley, 20, make show history by kissing his girlfriend's brother Nick Tilsley, played by Adam Rickitt, 25.
Actor Bruno Langley made Coronation Street history
Producers Granada received 16 complaints about the episode.
A Coronation Street spokeswoman said 12.5 million viewers was "about average" for the time of year, and the episode was not intended as a ratings-chaser.
"This was just the start of a story line which has a long way to go," she said.
On Monday, Channel 4 defended Derren Brown's controversial show against critics who accused it of glamorising gun culture.
"Gun culture is an epidemic and the issue is about why people are in possession of handguns rather than copycatting of a TV show," said a spokeswoman for the network.
"The bigger picture is more about what is going on (in society)."
She said there had been "a few dozen" complaints about the use of a gun in the context of the show.
A spokesman for Brown said the star was relieved the stunt was now over after many months of planning.
"He's very pleased with the reaction from the public. There have been so many people using his website to email him encouragement that it has actually crashed the site," said Brown's representative.
"He's even been getting emails from families saying that they enjoyed sitting
down together to watch the programme."
Its 2.9 million audience was about 400,000 up on Channel 4's normal 2100BST Sunday night slot - traditionally one of the toughest in which to win viewers.
The programme, recorded on a time-delay, showed Brown, 32, safely fire the pistol after a member of the public had apparently loaded it with one bullet in its six chambers.