OK, here's the argument to be made to people on the fence, and even to the antigunners: registered machine guns are tightly controlled, whereas unregistered machine guns are not. By having a closed registry, you encourage people to make illegal machine guns, or workarounds such as bump stocks.
I think it's pretty obvious to everyone, including anti-gunners, that people who would be willing to register their machineguns are not going to be the same people who will make illegal ones. The registry is not at all a concern for those willing to make illegal machineguns.
Bump stocks might be a slightly better argument, though still not a good one. People who see bump stocks as a problem are, in general, FAR more interested in banning bump stocks and further regulating semi-autos to deal with the "problem" than in making machineguns cheaper and easier to own. I can't imagine anything but incredulous laughter would result from proposing to an anti-gunner that making machineguns easier and cheaper to own is a good solution for reducing the proliferation of bump stocks.
I have to admit that there's strong logic to their position. If the perceived problem is too much firepower available to the general public, making it easier and cheaper to get firepower is a logically problematic response.
Why isn't the NRA openly making the case to the public?
Because the public has almost exactly zero interest in making machineguns cheaper and easier to own. As I said earlier, even the gun community is divided on this issue.
This is a common problem amongst the more die hard elements of the gun community. Many of these people have a strong tendency to come to believe that their viewpoints are mainstream. This results in loss of touch with reality and in significant misconceptions about general opinion. Reality is that many of their views aren't even mainstream amongst the general gun community, and the general public sees them as laughably radical.
Get away from your core group, ask some people who don't qualify as gun enthusiasts, or maybe who don't even own guns at all, what they think about the idea of making legal machineguns 10 times cheaper and about an unlimited increase in the number of legal machineguns. I'm serious about this--talk to some real-world folks and see what their views are. I think you'll be very surprised.
Something like the MG registry is a technical issue. The general public has virtually no impact on Congress regarding technical issues.
This is a case in point. To YOU the MG registry is a technical issue. To the general public, keeping machineguns heavily regulated and off the street is an emotional issue and they will interact with their representatives accordingly. The politicians understand this and therefore are not going to be amenable to having discussions with people who start out the conversation with statements like: "The MG registry is a technical issue." because that is not the reality that they must live and work in.
I'm not against the NRA. I want a better NRA...
Let's be frank. What you want is an NRA that mirrors your views.
1. The NRA has 5 million members, not just one member named AlexanderA. The NRA is going to represent their membership as a whole, not just you.
2. The NRA must still operate in reality. Even if all the members wanted exactly what you do, that still wouldn't give the NRA the power to do whatever it wants to because the NRA doesn't make laws. Congress makes the laws and there are another 320 million NON-NRA members who Congress answers to.
If the NRA is the most powerful gun lobby, then they should be responsible at least in part. In other words, do something with all the membership/revenue.
This is a false dichotomy. Just because the NRA is the most powerful gun lobby doesn't mean it can pass any legislation it supports or kill any legislation it is against. The NRA still works within the bounds of public opinion--or, if you prefer--within the bounds of Congress' perception of public opinion.
Remember, the NRA still has only about 5 million members--less than 2% of the population. They not only have to keep those 5 million members happy--and as I've mentioned a couple of times now, not even all of those members would support easier access to machineguns--they also are restricted by what Congress feels it can/can't get away with.