Got my vtac rail dropped off today so decided to fit it before work. I took the handguard off, tapped the pins out of the sight post and pushed it foreward. Got the fake gas tube out and now I'm stuck. I can't unscrew the delta ring assembly barrel nut/cog thing. I've had mole grips and everything on them and it won't budge. YouTube, who usually comes to the rescue has let me down as the King arms m4 doesn't have screws in the delta ring like some. I've soaked it in wd40 and swung on it with some vice grips. Even tried the screwdriver and a big hammer but I can't get it to move. HELP!