Georgia Gun Owners, with 13,000 members, has added 1,000 members since the Parkland shooting.
The National Association for Gun Rights, which claims more than 4.5 million "members and supporters" on its website, estimates its online membership applications have increased by 30 percent in the tree weeks after the shooting.
The Connecticut Citizens Defense League, which has a membership of almost 29,000, said it typically gets 15-20 applications a week, but received almost 200 in the week after Parkland.
Gun Owners of America, which claims 1.5 million members, received "hundreds" of new members in the wake of the shooting.
The Nevada Firearms Coalition estimates membership renewals and requests have increased by 20 percent since Parkland. It did not see this circle-the-wagons reaction after October's Las Vegas mass shooting.
Background checks: Clerks of court must upload at least weekly the names of people barred from owning guns because of a history of violent crime, drug use or mental illness.
'Red flag' laws: Ohio should have a law that allows police to take a person's weapons if a court decides he or she poses a threat.
Armor-piercing ammunition: Some of these types of bullets are illegal federally and would also be by Ohio law.
'Straw man' purchases: If you buy a gun for someone who is barred from owning one, match the federal penalty of 10 years rather than the maximum penalty under Ohio law of 18 months in prison.
Domestic violence: A person convicted of domestic violence or subject to a protection order should automatically lose the right to buy or own a gun. This would mirror federal law.
Bump stocks: Ohio law would codify federal regulations that will ban the device like once they are enacted.