President Trump's Tuesday announcement of a bump stock ban is upsetting members of a core constituency: gun owners wooed by his effusive campaign-trail vows to defend the Second Amendment, with two groups promising to see Trump in court.

"If there's anything that irritates you more than a president like Obama who's trying to stab you in the heart, it's one who is trying to stab you in the back," said Michael Hammond, legislative counsel of Gun Owners of America, a group that claims more than 1.5 million members.

Bump stocks allow semi-automatic rifles to fire more rapidly, contributing to the 59-person massacre at a 2017 Las Vegas concert, and the ban was widely anticipated. Owners have 90 days to destroy or give the government their devices.

The ban was regarded as a less-controversial gun control step after Trump shocked gun groups in February by endorsing a higher age limit for AR-15 rifles, background checks for private gun sales, and reforms to let police "take the guns first, go through due process second.”

Hammond, who branded Trump the "gun grabber in chief" when he voiced support for various forms of gun control after the massacre at a high school in Parkland, Fla., now calls him the "gun grabber in chief, with a vengeance," arguing the bump stock ban is illegal and opens the door to more weapon seizures.

"I don't think Trump understands that just because he goes to 10 rallies and says 'I love the Second Amendment' that if he does things that are dramatically anti-Second Amendment, our people are going to be mad. Our people are not stupid," Hammond said.

On Friday, Gun Owners of America intends to sue the Trump administration over the bump stock ban, citing the Obama administration's conclusion that the plastic devices don't meet the legal definition for machine gun, meaning they cannot be banned.

Hammond estimates that up to 1 million people own a bump stock and objects to the approximately $300 item being taken without compensation. He argues the Trump administration's legal justification could later allow for a backdoor AR-15 ban.

Another group, the Firearms Policy Coalition, filed a federal lawsuit Tuesday challenging the ban.

"The bottom line is President Trump has been more anti-gun in his tenure, in terms of legislation and regulations, than the Obama administration," said Brandon Combs, president of the Firearms Policy Coalition.

"I think his base is probably going to see in the next election cycle the choice between someone who has not been great for us and someone who would probably be worse. Then the question is, what would that mean for turnout?" Combs said.

The bump stock was banned the same day as Trump's Federal Commission on School Safety adopted a report calling for states to pass laws allowing the temporary gun seizures using "extreme risk protection orders." The laws would be aimed at disarming deranged would-be killers. Hammond calls them "gun confiscation orders" that could be abused by jilted exes, rationalizing sudden and dangerous police raids. He expects a fight in Congress over incentivizing state law changes.

Reaction to the new bump stock ban, however, draws a sharp contrast between hard-liners and other gun-rights backers, including of the National Rifle Association, whose leaders lunched with the president after his post-Parkland remarks.

The NRA issued statements criticizing the specific details of the bump stock ban and urging caution on extreme risk protection orders. But neither statement directly criticized Trump.

NRA spokeswoman Jennifer Baker expressed concern that the bump stock ban "fails to address the thousands of law-abiding Americans who relied on prior ATF determinations when lawfully acquiring these devices." The NRA had urged a grandfathered legality for existing devices.

Chris Cox, executive director of the NRA Institute for Legislative Action, addressed the risk orders in a statement, saying, "[W]e appreciate President Trump’s support for keeping firearms out of the hands of those who have been adjudicated by a court to be a danger to themselves or others in the form of state Extreme Risk Protection Orders — provided they include strong due process protections, require mental health treatment, and include penalties against those who file frivolous charges to harass law-abiding citizens."

Josh Blackman, a professor at the South Texas College of Law, said he doesn't see the bump stock policy fundamentally undermining Trump's pro-gun base, though he shares Hammond's concern that the ban could open the door to future liberal reinterpretation of gun laws.

"For most gun owners, this is not a big deal ... [but] this loose reading of the ATF statute that Trump used can be employed by President Elizabeth Warren to regulate other types of firearm parts that are far less controversial and far more commonly used," Blackman said.

Blackman, who submitted a regulatory comment on behalf of the Cato Institute opposing the bump stock ban, said he believes some gun advocates actually may be relieved, however. "I think the NRA is happy because this is better than legislation," he said.

Other advocates share Blackman's concern that Trump has blasted a path for future weapon seizures.

"It looks like Trump just caved into the demands of the gun grabbers and gave them what they wanted while throwing gun owners under the bus," said Erin Palette, coordinator of the Pink Pistols, a gay gun rights group whose litigation expanded gun-possession rights in the nation's capital.

"So far he has only banned bump stocks, which is troubling for a variety of reasons, but regulation on a niche accessory does not a gun grabber make," Palette said. "I think that nearly all gun owners regard bump stocks as range toys rather than serious pieces of shooting equipment, and their objection is based largely upon this ban being the proverbial camel's nose inside the tent and will lead to more regulations and bans."

The Trump-appointed school safety commission's report did not recommend a higher age limit for gun purchases, which Trump had embraced this year at a White House round table conversation with lawmakers, or other far-reaching changes.

But Hammond sees the glass half-empty.

"I'm feeling very put upon getting two very significant gun control hits in the same day," he said.

"If it were not a president who completely and totally owed his presidency to the Second Amendment community, maybe it would be a little different," Hammond added. "We for eight years battled the Obama administration. We were successful in killing every single statutory word of gun control. Now, lo and behold, we have this very dramatic call for gun control from the states and from the federal government — from an administration that we paid a lot of our time and treasure to elect."