What size neck would be recommended for an accurate varmint rifle?
Stepchild

If you are making your own barrel, I'd suggest measuring a loaded round, then the neck wall thickness. You can subtract a few thousandths if you're interested in neck turning all your brass for uniformity and close fit in the chamber. This is the most accurate setup. For instance, if neck wall thickness measures .012. A loaded round would measure .267" (.243 + .012 + .012).
To trim the brass to clean up uneven necks, you could go with .010" necks, making a loaded round of .263". Allowing .002" inch for chamber clearance, you'd cut the chamber to .265". You must, of course, be very careful to trim brass to fit the chamber, or disaster will result.
If you are having a reputable barrel maker or gunsmith build your rifle, I'm sure they can suggest the proper measurements, and it's probably based on the reamers they have on hand. I had Shilen build two for me and they were very helpful with such information. Tell the builder what you intend to use the gun for and the bullet weight you are most interested in and he can taylor the barrel to your specs.
One last thing, neck turning is tedious work and results in a fairly slim accuracy gain. I think if it were me I'd go with a minimum SAAMI chamber, and my groups would probably slightly larger, very slightly. A "minimum" chamber is cut to the tightest industry specs for the caliber.

[ 08-01-2003, 22:59: Message edited by: Bobby ]

Bobby,
Thanks for the reply. My cousin is putting a rifle together for me, the barrel is presently .243 Win., he has a friend with a .243 Ackley reamer, with a .262 neck. I turn my cases anyway, just don't know if I want it that tight.
Stepchild

Sounds like you've got a real handle on your project now. I wish you the best of luck with your new rifle.
Let us know how it turns out.

[ 08-02-2003, 01:31: Message edited by: Bobby ]