Remember, the pilot contacts the lands of the bore, not the grooves. Apply lots of oil to the surface being cut when facing or crowning to float away the shavings so they don't scratch the inside of the barrel. Now you can start squaring the end with the facing cutter. Here again, clamp the barrel in the vise with only a small portion of it protruding to protect it from errant file strokes. I like to mark the end of the barrel with a magic marker so I can watch progress and make sure that filing is more-or-less even or removing metal from specifically where desired. Once the barrel is cut off, do some initial cleanup and squaring with a file. Brownells said a lathe or saw is preferred, but you can use a grinder or cutting wheel if you take it slow and don't raise the barrel's temperature too much. That way you won't run the risk of scratching the 'good' part of the barrel if the hacksaw slips. Be sure to place the barrel deep into the vise so the upper surface of the barrel is below the upper surface of the vise (see the figure).
