I installed a DPMS 16" barrel (with the standard front sight post/gas block) on a YHM upper. Only thing not included on barrel I ordered was the Delta ring. Barrel has been installed per mil-spec, Delta ring and all. Now, is there any way at all to install the gas tube without removing the front sight post? I REAAALLY don't want to smash the pins or marr the color at all. I guess the next question is, what's a good touch-up for smashed up parkerized barrels?