Unrelated to the quote, here is a link to Sierra Bullets Manual 243 article:Forming .308 Win brass to .243 Win brass
« Reply #15 on: 11:58 AM, 05/08/11 »
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243W brass made from 308W could actually improve things if you're shooting a factory rifle. A loaded round using LC 63 GI brass reformed to .243 measures about .274" at the neck. A factory R-P .243 usually measures about .272". SAAMI specs call for a minimum chamber of .277" and a maximum cartridge of .276".
I don't bother turning the necks on my reformed brass, not even to clean them up. They are more than good enough for live varmint shooting exactly the way they come out the die.
If you are shooting a custom chamber you'll probably have to turn the necks regardless.
Ray