brett1868 wrote:The 222 Rem Mag is the parent case used to make the .204 Ruger and both have a case length of 1.850". While you can neck down a larger calibre to a smaller one, I'm not sure you can go from smaller to larger without the risk of splitting the necks. The .204 is prone to neck splits with Hornady factory ammo so maybe avoid their brass. Sorry I couldn't be of more help but maybe others can jump in on the practicalities of necking up brass. Possibly Bruce at Bertrum Brass may be able to point you in the right direction to locate it, if they don't already make it themselves (03) 5792-292.
wrong i ran a 6x45 for 15 years and never had a problem have mate that had 25 223 they never had a problem either you just have use your head