I will try to answer this but advise you to get a few G.I. Manuals. I have seen several ways to do it, some with the bolt and barrel out of the gun. This is what works for me. With the gun assembled, hold or lock the bolt back. Turn the barrel in to the receiver until the bolt will not go forward into battery. You can check this by releasing the bolt after turning the barrel in a few notches. You can turn the barrel from the rear with a screwdriver in the barrel notches. Once you get the barrel far enough in that the bolt will not go forward into battery, turn it out one notch at a time until the bolt will go forward into battery. Then turn it out one more notch and you are done. At this point you need to take the gun to the range and shoot it. If it seems sluggish, turn the barrel out another notch and try again. A lot depends on the ammo. I have found that different ammo may need one or two notches more or less then worked with the last ammo. If the gun is running faster then it did with the last kind of ammo you used, or you start getting case head separations, you may want to tighten the barrel a notch or two. You should definitely buy some books on the Browning MGs. Dolf Goldsmith has written the definitive series on the BMG. Long Mountain sells a book that has reprints of a bunch of BMG shop manuals. They are all worth getting. The 1919a4 web site is also very informative.