Maybe some of the more experienced builders will chime in, but I just did this twice and all I did was installed the trunion and bbl parts, aligned everything, clamped the bbl down really good, and ran it through a drill press with the correct metric drill bits (I think you'll need 4mm, 5mm, and 7mm; I just bought a set of them). I drilled fairly slowly using the bbl parts as a guide and throwing lube on the drill bit quite often.
Oh, quick tip- once you align the parts (very carefully), score a small matching line in the part and the bbl. That way you can check really quickly to see if you bumped it out of alignment right before you start drilling.
install barrel to trunnion, get headspace, drill and pin, the pin will be .277, you want to drill a few thou smaller, then use a reamer, put the pin half way in, next get the RSB, gas block FSB ready to install, use a little jb weld when you press these on, align everything, let set over night, the jb keeps everything in place when you drill and press the pins in, once this is done, you can remove the barrel from the trunnion and do the riveting