You'll need a bit of barrel length or you will achieve not much more than your old 260 in way of velocity. Robbie has done a few 6.5x55 to 6.5-284 from memory on Tikka's. To re-chamber a Tikka he needs to be able to cut a reasonable amount or else it doesn't clean up well, as Stug said the barrel steel is very hard. Start with a long action so you can seat those 140 VLD's out where they belong.
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