I plan on building a 20" 1/7 govt profile flat top and I have seen barrels advertized with standard and "F" marked FSB. What is the difference and which is the correct one for use with the sights on a removable handle/rear sight assy?
C & R FFL 03
F for flat top upper.
The base (where the front sight post goes) of the F marked Front Sight Base is about 0.040" taller than the standard.