Problems removing gas tube
OK. I've got a RRA upper with a barrel I can't stand. I've decided to replace it with something better. Part of my purpose is to get some experience with AR maintenance; I've never changed a barrel before. I've gradually acquired all the tools necessary, but I need some tricks.
I got the gas tube retaining pin out easily and now comes the tube ... which will not budge. I've tried pulling, I've tried clamping with several different sets of pliers and hammering the pliers toward the receiver, I've tried spraying the exterior of the tube at the points where it contacts the FSB and the receiver, and all I have is a scratched up tube that has not shifted one iota.
It appears that the tube is tight in the FSB. Should I remove or loosen the FSB (I wasn't planning to)? Any suggestions or references I should look at?