I have built many lowers but no uppers. I'm in the process of building an upper from parts now but have I am confused about the FSB & barrel - If the FSB has the grooves for taper pins do I still need the taper pin grooves on the barrel? I don't want to buy a stripped barrel and then pay to have the FSB installed. If that's the case, then I should just buy a complete upper with barrel assembly, right?

Please excuse my newbie-ness on this.

Thanks
DR

Yes, the barrel must have the grooves drilled in addition to the fsb being drilled.

The FSB and barrel are drilled together as a set when manufactured.

http://www.ar15.com/forums/t_3_4/226782_Assemble_your_own_LOWER__UPPER__FREE_FLOAT__TRIGGER__GAS_BLOCK___Step_by_step_instructions_.html&page=25#i5724417

Youtube Video

Ok thanks guys!

Easier to just buy your barrel with the FSB already installed.
Drilling, reaming and pinning a FSB CORRECTLY is not a casual task.