Mounting a 1.5X5 scope on upper with A-2 Front sight.
Purchased a Daniel Defense upper with a A-2 front sight/gas block. I have also purchased a Yankee Hill gas block with a fold over front sight. Viewed a number of video about how it is done. My main problem in my mind is that the factory A-2 has some black stuff sealing the unit to the upper. I am afraid of not being able to loosen the A-2 without damage to my barrel. Any suggestions on what I am getting into. Is that black stuff easily removed?