Libertarianism and anarcho-capitalism seem like they would be naturally aligned philosophies. In our very state-run world, they firmly agree on one thing: by exercising power at gun-point (as all governmental action does, on the most basic level), government is abrogating the natural rights of the people under its influence; and here on our pale blue dot, there are precious few places outside of that influence. Even in the middle of the ocean or high above the Arctic circle where you're the only soul for hundreds of miles, you're only outside of government influence as long as you stay unnoticed and stay out of the way of the massive, intercontinental powers that be. In such a world, firmly lodged as it is in the 'authoritarian' end of the spectrum, cooperation between libertarians and an-caps for the mutual benefit of a more free existence can and should be the order of the day.
This, generally, is the case. Despite clear philosophical differences between the two camps, libertarians and an-caps have a mutual enemy to fight. However, a tendency can and does develop on both sides to dismiss the others. Libertarians, when pressed to explain why they don't jump a little further on the political spectrum and adopt anarcho-capitalism, are likely to say something like "I think trying to do away with government entirely is both highly improbable and foolish. An-caps must admit that, for a few very simple practical problems, government is unfortunately the best answer". This, of course, infuriates anarcho-capitalists, for whom government (or any use of force) is always unacceptable, no matter what, period. They then retaliate by suggesting that libertarians are "no better than the statists, because imposing ANY government power is immoral". These points of contention can lead each side to the conclusion that the other is naive and unreasonable. Practically speaking, time spent recruiting a libertarian to anarcho-capitalism is time wasted, and vice versa. There are far bigger battles to be fought against far more numerous opponents for that sort of in-fighting to be productive.
My purpose, then, is to remind both sides that while there are philosophical differences, the reality of the world we live in requires them to be political travel companions, moving slowly against the headwinds of authoritarianism. It will likely be a very long, very tiresome journey, and bickering can only slow us down and make the journey very unpleasant for both sides. Some find that their morality, their freedom, are an "all or nothing" affair. If you advocate a little use of force, you're no better than the individual who advocates the use of much force. This absolutist approach can and will only be frustrating and exhausting. Our society will only move slowly away from authoritarianism, and by the time the paths of libertarians and anarcho-capitalists diverge, much will have changed for the better. Some may disagree, but as a libertarian and fellow traveler, I would much rather take a small step towards freedom and claim a small victory than refuse to move at all because the entire venture isn't being taken all at once.
If there is one thing we should all agree on, its that by the time we have realistic cause to disagree, the world will be a much more free place.