Re: Barrel Work in a Lathe
Flat strips between the 4 chuck jaws and a barrel breech do not make for much gimble movement. If the chuck jaws are not parallel to the spindle bore the spider will just bend the barrel to make up the difference. The barrel will seem to be dialed in on both ends, but it is not the best. This is why some use a wire wrapped around the breech or a right side of headstock spider [like HateCA just said].
A spud in the breech that can be dialed in over some length will assure that the bore is locally parallel to the spindle, even if the barrel came a little bent from the factory.
But there are two levels of separation between my above nick picking and reality:
1) Off center chambers put the bullet in the bore with a center of gravity off the center of the bore, and centrifugal force causes the bullet to fly off the center of the bore at the time of bullet escapement. Unlike handloads where the eccentricity is randomly inserted and causes inaccuracy, the off center chamber is consistent and mostly throws the bullet off center to the same small group.
2) Shilen pre chambered barrels are long chambered, and only need some shoulder and breech cut off to fit the action for headspace. The bolt face might not be perpendicular to the bore, possibly causing inaccuracy, but this error would likely be very small over the width of the case head.
What does it all mean?
If that is a Stainless Shilen, you can likely HAND FILE off the breech and shoulder to fit, and get 1/2" groups.
You must ask yourself, "Do you want to be a fanatic or not?"
