I have a M400 and taking the FSB off is no easy task for a beginner (myself included). It is press fit and the pins are ridiculously tight. I ended up using a Dremel w/ mettal cutting wheel at 30K rpm and VERY CAREFULLY cutting the FSB perpendicular to the barrel until it cut into the pins themselves. At that point, both pins had a fresh gorge running their entire length and I was able to tap the pins out. After that it was just a matter of removing muzzle device, removing the FSB, removing the barrel, removing the delta ring (lots of people just cut them off), installing a DD low-profile gas block, re-installing the barrel and then mounting a Troy Alpha rail. I was brand new to anything of this nature so I read a lot online and purchased a ton of armorer's tools in order to do that job right.
Recommended items (at least for me):
-Punch set
-Dremel
-Metal cutting wheels
-Receiver vice block
-Barrel nut wrench
-Wrench for muzzle device (if necessary) - one came as part of the barrel nut tool on my setup.
-Red loctite (if you are going to use a clamp-on lo-pro GB)
-Moly grease for the barrel nut
-Torque wrench
-Brass drift (for massaging the Sig FSB off the barrel)
-Lubricant (to keep the barrel from getting scratched up while removing the FSB.
It's not rocket science. Just study up, equip yourself with the correct tool and go to town!
Here are the results:
https://lh5.googleusercontent.com/-T...925_223556.jpg