Many are grass-roots organizations formed in the last few years because the powerful National Rifle Association was too busy, or too big, to help fight city and statewide gun laws. The constellation of smaller splinter groups are more aggressive and will play a leading role in hashing out the scope of the Supreme Court's latest ruling supporting gun rights, in part by filing lawsuits at the local level.
The nation's highest court ruled this week that Americans have the right to own a gun for self-defense anywhere they live, a ruling that certainly means the end of Chicago's 28-year-old gun ban, and the justices left a lot of room for lower courts to determine the exact limits on gun laws.
The ruling comes as states across the country have loosened gun restrictions over the last 2 years. Even President Barack Obama signed a law that took effect earlier this year allowing firearms in national parks.
While the NRA entered the latest case only after the Supreme Court allowed them to join, the nearly 138-year-old group has been reluctant to wade into other legal battles because they have for years been on the losing end, said Eugene Volokh, a UCLA law school professor who has written extensively on Second Amendment issues. In that vacuum, smaller groups have exposed a tactical advantage by drafting talented and passionate attorneys who are often willing to file pro bono legal challenges.
"Twenty years ago, Second Amendment litigation was seen to be a hopeless matter," said Volokh. "It has been said that the NRA was quite skittish about filing big-picture, Second Amendment cases because in part they were around when they were always losers, and they'd get smacked down."
The NRA is by no means struggling. The group said its membership has surged 20 percent since 2007 to about 4.1 million members, and many politicians from both parties still clamor for its endorsement.
"I don't think anyone can be everything to everyone," said NRA spokesman Andrew Arulanandam. "It's a testament to the strength of the issue, the number of individuals out there who believe in their Second Amendment rights."
The smaller groups are more flexible, often don't have much overhead costs because they rely on the Internet and exploit their ties to the community.
In Wisconsin, Nik Clark helped create the gun rights group Wisconsin Carry in November because supporters felt the NRA didn't support legislation that would allow gun owners to carry concealed weapons. The group quickly expanded beyond that issue, filing a lawsuit in January challenging a 1,000-foot, gun-free zone around schools - an issue the NRA has yet to embrace.
"We formed to take up issues that not just the NRA, but really anyone, wanted to touch," said Clark, the group's chairman and president. "And we felt there was an opportunity to do something no one else was doing."
Ed Stone helped set up GeorgiaCarry.org in 2006 when he grew tired of unsuccessfully urging the national organization to speed up Georgia's licensing process and help convince lawmakers to lift more restrictions on where gun owners can carry their weapons.
"In spite of many people asking the NRA to address these issues, the NRA ignored them," said Stone. "With 4 million members or so, I would guess that the NRA gets too many requests for help to be able to offer assistance to all of them. In my case, I started looking around asking, 'If not me, then who?"'
His group has become a force in Georgia politics. It pushed a sweeping gun rights expansion through the state Legislature this year and has filed a flurry of litigation, including a federal challenge that sought to allow firearms in parts of Atlanta's busy airport.
Calguns, an advocacy group in California, is making its mark by catering to a younger generation. It started in 2002 as an online sounding board for young gun owners, and now raises money and sponsors litigation.
"There's a bit of a generational gap. The NRA is older and grayer, and the Calguns community are people who are in their 20s and 30s and 40s," said Gene Hoffman Jr., the foundation's chairman. "You have to adapt to your community, and we have a very unique environment. We've had to be a lot more creative with litigation and the overall political message."
One example: Some 30 Calguns members marched at last weekend's San Francisco gay pride parade with pink pistols, chanting "Marriage license! Carry license!" It was all an effort to appeal to a new group.
One of the most influential upstarts is Opencarry.org, which this year led a high-profile campaign to urge Starbucks and other retailers to allow gun owners to carry their weapons openly within the stores. The NRA never endorsed the campaign.
"The NRA has, by necessity, had to focus the vast majority of their resources over the last few decades at the federal level," said John Pierce, who co-founded OpenCarry.org in 2004. "They're focused on general gun rights, what we can do to protect the most gun owners."
The NRA's Arulanandam said the organization has fought for the right to carry concealed weapons - although some critics say the group isn't doing enough. It has also helped push legislation across the country that requires officials to issue firearms permits to people who meet requirements, stripping them of discretion. The NRA also supports pre-emptive legislation that reaffirms Second Amendment rights.
The group showed its influence last month when NRA lobbyists persuaded the Democratic-controlled House to exempt it and other large interest groups from identifying top donors.
"On any given day, the NRA is the only entity that is fighting at every possible level - the legal level, the international level, the federal level and the state and local government level. Our challenges are multiple because we're active on multiple playing fields," Arulanandam said.