RE: Barrel length- .257 Roberts and 7mm-08
You can always shorten the barrel if you don't like the longer version. Start with a 24 inch barrel on either one of these calibers. 24 seems to be the best lengh for velocity. A gunsmith friend and I took about ten surplus 6.5x55 rifles and cut the barrels off one inch at a time. They started out at 29 inches. All of them gained velocity as we cut the barrels off. This until we reached 24 inches. At that point the started loosing 25-35 fps per inch. We ended up leaving them all at 24 inches.