" NRA: Practice Range," released Sunday, is billed as "the NRA's new mobile nerve center" with access to information about gun safety, legislation and news from the influential 4.25 million-member US gun lobby group.
But its main feature are shooting ranges -- some with vaguely coffin-shaped targets -- and a choice of handguns, rifles and shotguns, including the type of assault rifle used in the Newtown school massacre in December.
Players have one minute to pick off as many targets as possible, then post their scores on a leader board open to all.
"Is this some kind of sick joke?" wrote one customer in the review section of the game's App Store page.
"The NRA complains about violent games and then releases one a week later. Sure you're not shooting at humans but does it really matter? F***ing ridiculous."
But in a reflection of how guns divide Americans, others gave the app five-star reviews.
"Freaking awesome," wrote one satisfied customer. Another added: "Better hurry and download this before they take it away from us."
As news of the game spread, an online petition was launched on SignOn.org urging Apple chief executive Tim Cook to withdraw the app, which is rated as appropriate for youngsters as young as four years old.
"In no way is this shameless and disrespectful product appropriate for children even younger than the Sandy Hook victims," said the petition, which by mid-afternoon had gathered close to 300 signatures.
The game's release coincided with this week's SHOT convention, an annual trade show for the shooting, hunting and firearms industry organized in Las Vegas by the National Shooting Sports Foundation, a gun industry trade group.
The foundation happens to be based in Newtown, Connecticut, where Adam Lanza, 20, cut down 20 children aged just six and seven, along with six teachers at Sandy Hook Elementary School on December 14.
Lanza -- who had earlier shot and killed his mother, owner of the Bushmaster assault rifle used to kill the children -- also took his own life in one of the worst mass shootings in US history.
While President Barack Obama launched a task force to look into tougher gun laws, NRA executive vice president Wayne LaPierre blamed "vicious, violent video games" and the wider entertainment industry for such bloodbaths.
Separately, 52 percent of respondents to a Washington Post-ABC News poll said the Newtown shooting had made them more supportive of gun control.
The poll also found broad support among both Democrats and Republicans for mandatory background checks for those who purchase firearms at gun shows. Such events are said to account for 40 percent of all US gun sales.
Prospects of tighter gun laws from the Obama administration -- which in its first term did nothing to renew a ban on assault rifles that lapsed in 2004 -- has seen a buying frenzy for firearms and ammunition.
It has also seen the NRA pick up 250,000 members in just a month, the US News and World Report website reported.
"I would say that every time President Obama opens his mouth... about gun bans and restricting the rights of law-abiding Americans, people pa
