Re: Chasing the lands
As far as you have too when chasing accuracy. I would go until it stops shooting accurately. You don't have to re-barrel it, you can have a gunsmith trim a 1/4 to 1/2" off the chamber end of the barrel and then rechamber it. The rechamber job will clean up the old chamber/leads and put you back at square one. You will have to readjust your loads overall length(s) and may have to start over on load development.
As for how far out the bullet can be in the neck? When I was loading 40gn Ballistic Tips (tiny, short bullets) in my .22-250Rem, they never would touch the LaG's. I did some research (Google search!) and came up with 1/2 a caliber in the neck. So I kept 1/2 of .224" (.112") in the neck. This kept the bullet "close" to the Lag's but also kept the bullet runout low. Hope this makes sense and helps. JohnnyK.