Man, I was excited to see this thread bump back up. Thought for sure I would get some input on cutting the chamber and ideal number of grooves.
Oh well, that brux sounds nice.
Again watch this. Measure your magbox's inside diameter and subtract at least .050" and make your dummy round to this length. For the dummy round, pic the longest sleekest higher BC bullet that you will reload and throat using that bullet.
That way the throat will in fact be SHORTER not longer and will kiss all other bullets of less sleek profile and factory ammo because shorter stubbier bullets move the ogive up the bullet. The opposite is true for the high BC bullets, the ogive moves down on the bullet giving you a shorter throat.
I would then call Lilja and ask for a 1-8" twist 6.5 caliber blank with whatever grooves he suggests. You can't go wrong and it doesn't really matter what grooves you choose. Copy the factory contour or if you like extra weight at the muzzle ask for his slightly bigger contour.
That's what I would do anyway, good luck with your build.
