False Muzzle

[Nuclearcricket]

Ok, went and got the mind sharpened up, dug out my trig book and crunched some numbers. I used .454 for a diameter as I was not quite sure what would be the best the bore or the grove so I just went down the middle. For a twist I used 18". That gave me an angle of 4 deg 32 min. If you were to cut the barrel with a wife EDM I figure you would conservatively loose a total of .020". That would give you a misalignment of .00158", probably not enough to really worry about. If you used a standard steel part off tool to cut the barrel off with I used .140" as a total loss and that would give you a misalignment of .011".
Hope this is of some help to you, or at least gives you some food for thought.
Sam