Regarding gun rights (leaving aside the constitutional constraints), the issue is both practical and prudential. If access to guns leads to more violence, or the kind of violence that is particularly destructive of social bonds (i.e., gun mass murders), then we should limit or eliminate gun rights. You, as a libertarian, would presumably say that you don't care about the consequences of gun ownership -- even if it is destructive -- because your ideology has determined that people have the right to own guns. I find that irrational and extreme. Now I understand there is a genuine issue about the facts, but like I say, even assuming the facts were as I think they are, my understanding is that libertarians would care: the "right" to own a gun outweighs all other considerations.
As to health care, I suspect, again, that the vast majority of self-identified libertarians are against universal health care even if it were absolutely demonstrated that it is more effective and less expensive than the dysfunctional private system we have. So again, even if you're personally being rational and you see the issue in practical terms, I sense a resistance to facts and actual social consequences by libertarianism which I find appallingly irrational.
I'm not appealing to the No-True-Scotsman fallacy, but are you sure your position really represents current libertarianism, or rather just good public policy informed by some basically sound values about the limits of government? Because I don't see your kind of rational analysis coming from most self-described libertarians, even those on the national scene.