I would like to get and idea what the powder capacity is of the 22-250 case necked up to 6mm as well as the ease of forming brass. This cartridge could also be formed from 250-3000 Savage brass but would not normally be done due to the inexpensive avalibility of quality brass.
There was a writeup in Precision Shooter magazine a couple of months ago about this round and it appeared to be just what I want in a 6mm cartridge for High Power competition.
Just looking at a couple of charts gives me the idea that it has about 5 or 6 grains less capacity than the 243 Winchester cartridge which would be just about perfect for using Reloader 19 and 95 grain Berger (OR Sierra) match bullets.
Anybody have any knowledge and/or comments about this round?

The 6mm International has been around for at least 40 years...

There is loading data for it at http://stevespages.com/page8c.htm

As an alternative you could try the new 6x47SM (Swiss Match) which uses 38gr of propellant to get 2,788fps from a 105gr A max. If you like I can send you the e mail adress of the firm.

Bruce,
I know this doesn't answer your question, but another option you may want to look into is the 6mm X.
Many high power shooters are using the 6mm X. This round uses 22-250 brass in a 243 win die cut .130 short. This gives you the case capacity and velocity you are looking for as well as the extra barrel life a High power shooter needs.
The 6mm X and the 6mm International are similar in capacity and performance. I believe the reason for the 6mm X's popularity is that 243 win dies are cheep to obtain and modify vs purchasing 6mm international dies which are high $$$ class "D" custom dies.

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J.W.
Hero of the Hapless
Master of the Obvious