When Texas Senator John Cornyn introduced a bill on August 5 that would incentivize mental health records reporting to the federal gun background check system (NICS), the backlash was swift. Backed by the National Rifle Association, the proposal was slammed by gun violence prevention advocates, who claim it will allow more mentally ill people to get guns. But there was another, perhaps surprising source of criticism: pro-gun groups.

“Are gun owners about to be betrayed by Republican leadership in the Senate?” The National Association for Gun Rights (NAGR), an NRA rival, wrote on Facebook. On its website, the group warned its supporters:

“This latest gun control proposal could result in more law-abiding Americans losing their right to self-defense … [and ] … coerce states to hand over your private medical records to the Federal Government.”

Among the 1,100 comments on NAGR’s Facebook post — most calling the bill’s supporters “RINO”s (Republican in Name Only), traitors, communists, and socialists — one reader wrote, “Enemies to the country and the constitution by law are executed. This is why we need and want guns.”

“The establishment gun lobby supports gun control,” NAGR added in the comment thread.

NAGR is based in Colorado and run by Dudley Brown, who also runs Rocky Mountain Gun Owners. The organization was founded in 2000 by direct-mail expert Mike Rothfeld. The NRA, which is considered the less extreme of the two groups, once called Brown “the Al Sharpton of the gun movement.”

Hard-line gun-rights groups accuse the NRA of employing an “if you can’t beat ‘em, join ‘em” approach to legislation, opting to shape bills and leave pro-gun fingerprints rather than risk being shut out of the political process. It’s unclear whether Cornyn’s bill was planned before the push for gun reform that has followed this summer’s mass shootings. But to some Second Amendment absolutists, it indicates the organization is pandering to the “gun grabbers.”

Several branches of the “citizen-led” Gun Rights Across America responded in similar fashion: “Why does the NRA back these RINOs and why do they keep selling gun owners out?” one post reads. “This is why i am NOT a member,” wrote one commenter.

The Second Amendment Foundation, which reports over 650,000 members, did not acknowledge the bill on its website, Twitter, or Facebook pages. Gun Owners Of America, a “no-compromise national gun rights organization” with a reported 300,000 members, posted an Associated Press report about the bill on its website. It was labeled as an op-ed.

The NRA seems to have felt the heat: The gun group has deleted a post linking to the same AP report on the legislation (hosted on the conservative website The Blaze) from its NRA News Facebook page. A later post on NRA News’s Facebook page, conveying the gun group’s official endorsement of Cornyn’s legislation, attracted another round of criticism from followers. The NRA did not respond to a request for comment.