Its probably glued in. The best way is what was mentioned. Use the point of the soldering iron to heat the bolt. Keep in mind that the butt sleeve, cap and any ring work are also glued. I'm thinking that with the amount of heat you will generate with the iron, it probably won't be an issue but why take chances. Wrap a damp paper towel around the butt sleeve to keep it a bit cooler. Let it warm for a bit and try it. Keep warming until you feel it move.
Once you can feel it budge, keep going on it until its out.
Once the bolt is out, you'll probably want to run a tap down the hole to clean out the threads if you are going to replace the bolt with another. If you work in a machine shop, you'll have a tap hopefully.
If you are replacing, most likely you won't have to glue it back in. If you find it necessary to secure the bolt, a tiny drop of silicone caulking near the top of the head is all you need. Just enuff to keep it from coming loose and not enuff to give you grief if you want to change it in the future.