Originally Posted by LittleRedToyota
the first thing that comes to mind is that you might have the wrong front sight base.
you should have an "F" marked FSB to work with a flatttop upper and folding BUIS. however, there are a number of manfucturers out there that ship flattop ARs with regular FSBs (that are meant to be used with a fixed carry handle).
the "F" marked FSB is a bit taller...so, if you don't have one, you have to dial the front sight post very high to make up for the shorter FSB.
check your FSB for an "F". what brand AR do you have?
Dude, he's using a TROY FRONT FOLDING BATTLESIGHT .
OP, can you post a pic of your front sight post so we have an idea what you're working with?