Earlier quoted context omitted.
I disagree. The NRA has 4 million American members which I think makes it the largest lobby by membership. I doubt they're all pawns of the gun industry. If the NRA wanted to solely juice sales and sell more guns they would give heavily to elect more Democratic candidates. The current presidency has been great for sales [0]. 0 - https://www.fbi.gov/about-us/cjis/nics/reports/nics_firearm_...
Left-wingers ranting about the "gun lobby" are like right-wingers ranting about the "LGBT lobby". Everybody loves to pretend that the opposing political party is driven by some strange, inhuman machine, not by a bunch of normal people pretty much just like themselves.
(I consider myself to be a right-winger, as I am certainly pro-gun and pro-business, and straight as a rail, but I never heard about LGBT lobby concept, except in jokes about fashion. LGBT guys and gals are fun.)