Im playing with a 6.5 SLR for 1000 yard BR right now.
The problem....ie the problem for me is the 6mms are hard on barrels.A 243 or a case close to a 243 in 6mm is tons of fun.But require more tuning and time than I care for.
Now you take a 6.5 at the size of a 243 case.... say a 260 and 2000 rounds of decent accuracy can be had.
http://www.6mmar.com/65_SuperLR.php
dave

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Only accurate rifles are interesting.