I had to use a hammer, punch, file and drill to get mine out. It took 30 minutes.
After failing to hammer it through, I hammered it enough to file the other side, then bashed it through the other way and filed that end off.... once the hand guard was off I drilled the pin out of the gas tube.
I replaced the pin with a 5/32 roll pin. I hear brass nails work well too.
Good luck.