I dont want to do the permanent mounted flash hider on an AR. I did that on my Mak90 but i dont have a Front site to mess with on it so it was not big deal. On an AR if i had to ever remove the FSB i would be screwed.
I would want around 14" over all after the brake is on so I am thinkin 12.5-13" actual barrel length probably i will have to look at it and determine exactly what length i want.

Another question, If i register a lower as a SBR can i buy any short barrel upper i want for it after that. I.E. can i get a 10" 9mm upper if i want? As long as it only goes on that upper.

sorry for the questions I am a newb on this stuff and want to do this the legal way not billy bob with a hack saw way