Besides, the "core mission" of the NRA isn't protecting the Second Amendment. The NRA is, I believe, a 501(c)(3) organization. That means "not-for-profit, educational." The core mission of the NRA is education -- firearms safety education, and marksmanship education.
I lobbied for a living for a decade. You are voicing a common misconception and have it totally backwards. NRA is almost all c4. A C4 can do all the lobbying it wants. It can be 100% hard core lobbying:
Federal rules on lobbying Activities by 501(C)(4)s
Tax Code A 501(c)(4) may conduct unlimited lobbying without jeopardizing its tax-exempt status as long as the legislation that the organization attempts to influence pertains to the purpose for which it was formed. Lobbying may be its sole activity. Specifically, lobbying includes:
drafting legislation;
persuading legislators to introduce legislation;
circulating lobbying materials to assist in the passage or defeat of a bill;
engaging members and the general public by letter, phone, or the mass media to encourage their legislators to support or oppose legislation; and
supporting or opposing referenda, initiatives, and other public ballot measures.
Before proceeding with these activities, however, it is important to check federal, state, or local lobbying disclosure laws and, in the case of ballot measure activity, disclosure laws for any registration and reporting requirements. A 501(c)(4) must notify prospective contributors that their contributions are not deductible as charitable contributions.4 This notice must appear in all written and oral solicitations.
https://www.bolderadvocacy.org/wp-content/uploads/2012/10/The_Connection_Ch1_paywall.pdf
if you look at case law on "purpose for which it was formed" NRA general organization easily qualifies, NRA's Federal NTEE Classification is "Civil Liberties Advocacy" and its Federal NTEE Tye is "Civil Rights, Social Action, Advocacy" which puts "purpose" squarely as advocacy
From a legal and general perspective NRA groupings are better set up to do policy advocacy and lobbying than any other groups. NRA, as (several) c4s, plus small c3 (civil rights fund), plus PAC is really well set up for that. I haven't checked if it has a 527. The large membership makes it the most legitimate and effective at lobbying, because it can legitimately say it has x number of people in a given US Congressional or state assembly district.
GOA, like NRA is c3+c4 (GOA looks to have 50,000-60,000 members according its 990 dues:income). It can do plenty but obviously has less credibility due to small size. SAF is as far as I can tell a c3 charity. SAF doesn't do legislation really, they subsidize paid legal work, and also arrange pro bono legal support in 2A cases in the courts. charities can do that all they want without problem from the IRS
The local/state local 2A groups are all c4 like NRA, a couple of the larger ones are twinned c3/4
So: c4 (dues and donations are not tax deducible) can legally be entirely IRS defined lobbying. c3 (donations are tax deductible) can be entirely issues advocacy (“education”) but c3 has to limit its actual work on specific legislation to less than a substantial amount (generally under 20%). C3 rules are:
https://www.irs.gov/charities-non-profits/measuring-lobbying-activity-expenditure-test
The gun control lobby does a higher proportion c3 funding than the pro-2A side. Soros and Bloomberg have made an art of it.
For example for the gun control groups can do the following under c3 (tax deductible charity work): Busing kids into DC, giving them signs, feeding them, putting them up in hotels, buying them all shirts, arranging permits, hiring entertainment, playing celebrities to be there, educating the kids on general talking points on gun violence tolls for when they go see their member of congress would not be "lobbying." If paid staff from Moms goes to the Hill office with them -- and the staff mentions specific legislation -- that would be lobbying, but even a c3 can do a bit of that.
I know this worked for a twinned c-3 plus c4 where I did a lot of advocacy and some lobbying. I used to journal the time I spent talking to hill personnel about specific legislation. You could spend a month advocating policy and get your time on actual legislation down to <5%, easily -- and the limits are higher than 5% anyway. This meant this could internally be billed almost all to the c3, which is monies twice as easy to raise, since they are both corporate and individual deductible, and also pass though if you can get a foundation to give you grant money.
This is why every year more and more advocacy is done by foundations. Hundreds of millions of dollars, maybe more of issues or policy advocacy is done by tax deductible foundations and charities. non profits like c4 that are NOT charities can do even more.
We ran all of the following though our c3 (all tax deductible)
1. conferences on policy and legal issues including all venue and speaker fees, publication, video production and distribution of the conference materials
2. junkets for members of media on whose beat we were
3. conferences for our members on how to lobby, talking points
4. report card on how people voted
5. meetings of staff with people from State, Commerce, Pentagon, NSC or white house don’t count as lobbying for the IRS either .
6. "Grants" to working journalists
7. placement of grad students in think tanks
8. a lot of other things I won't mention here
We also spent staff time in congressional offices or on the phone promising reward or penalty in member electoral support for co-sponsoring, voting certain way, or amending, or opposing specific legislation – that is lobbying -- but journaled our time and resources spent on that.
