I want to replace my FSB on my Armalite m15a2 post-ban with a no-ban version.  I noticed my current FSB has allen screw in it and the one Armalite offers (no-ban) use pins. Why? Is this something I can do at home or should I send it out? I already plan on having ADCO replace the muzzel device with a A2 hider. What do you thing I should Do? If I can do this at home how do I do it and where can a good FSB other than Armalite?

Have ADCO replace your FSB.  The only way you should attempt this yourself is if you are replacing it with another set-screw type.  The taper pinned FSB's need to be installed on a jig, drilling the barrel and FSB together, with a special bit..... and should only be installed by a competent gunsmith.  Too much trouble and cost just to add a bayo lug.... IMHO.  Spend too much money, and you could just buy a new barrel.

Where can I find the screw type that is currently on the Armalite but in no-ban. Where can I find an Armalite 20" HBAR barrel (no-ban) or who makes it for them? THANKS!  

You could tap the holes and add set screws from your old fsb  on a fsb that has a bayo lug on it.  there is an instructional website out on the web.   I did a google search and found it.  Heck I'll look it up and post it.  You are lucky that your barrel has flats.   My take off barrel that I threw on a LAR blemished upper had taper pin.   I put as much windage as I could and still couldn't get a zero.  I am lucky to have a 100 yard tunnel to test ammo in here in Wichita.
http://www.gswagner.com/arsight/arsightmods2.html