6.5-08 is fairly easy to do - a .264 instead of a .257 and a great cartridge, much better than a .243 for bullet weights and far superior SD. Very cool cartridge. Never seen anything in the .25 version but the "Page Super Pooper" or whatever Warren Page called it is a natural for a shot out .243 and can launch a 117 gr bullet to easily 3000 fps. There's another version, a rare one, the .257 Durham Jet that's made by necking up the .243 and utilizes the classic Ackley shoulder angle of 40 degrees, then the neck is shortened .300. This one is suppose to be capable of pushing a 117 gr bullet to around 3150. If I ever burn out my .243 it's gonna become a .25 Super Pooper.