Re: trying to build a new gun but cant decide
Shooting comp is about a lot more than energy.
The rifle and shooter must be able to perform in repetition, and a lot of it, whether shooting for score or for training. This is where the magnums fall short. They generate too much barrel heat and wear, and fatigue the shooter to an unnecessarily harsh extent.
For 6mm, the largest chambering I'd shoot would be either a .243 Win, 6BRX, or a 6XC. For 6.5mm a .260 rem, for 7mm a 280 Rem, and for .30cal a .30-'06. All of these will ring steel very convincingly out to 1Kyd and beyond.
More than these I'd consider neither necessary nor advisable.
Magnums are in their proper element when irresistable terminal energy needs to be delivered. The smaller chamberings do better when the primary goal is shot placement.
Greg