It seems the NRA is winning the argument more so because their message makes more sense to more people, and the gun grabber's message makes less sense to more people by comparison, than because the gun rights lobby is unified.
Look at the gun grabbers message, what is the main reason to limit access: "what do people really need a "bushmaster" style gun for anyway"? Well, that's not a reason, it's a question. And ultimately the response is "what business is it of yours what type of firearm I choose to own"?
Then they use Sandy Hook to justify their question; "if the punk @zz who committed the shooting hadn't been able to get his hands on one he wouldn't have been able to kill so many innocent people".