AR gas tube removal question

i am trying to take apart an Aero Precision AR15 but have run into a problem. I cannot get the gas tube out of the front sight base even though the pin is removed. I believe that there is simply a carbon build up holding it in, but am not sure. I know there is a simple fix but I cannot think of one. I would rather not tear up the gas tube as I would like to reuse it. Any ideas?

That worked like a charm. Thanks!