Not to completely derail this excellent 25cal discussion but I feel the need to keep you from making the 6 o'clock news.
To start.... military designation for that dumpster fire is 6.8x51. Kinda like the 7.62x51 but with a smaller and lighter bullet and a ton of proprietary case design.
So your hypothetical cartridge is going to have 115,000psi?? Um no bud. The hypothetical military round that the tacticool guys are drooling over is an 85k psi load that has a NON-RELOADABLE CASE with a stainless steel case head and primer cup. And is chambered in a proprietary rifle with a proprietary recoil system. High pressure in most modern firearms is 65k psi. So good luck necking down a case that is not re-loadable and that is only available to certain branches of the military AND THEN put it any commercially available bolt action rifle and touch it off. Your necked down 257FURRY cartridge would have somewhere around 105k psi!
Now if you are going to start with the civilian 277furry that is used in the sig cross rifle. its a neutered 58k psi load. The case is 100% brass and would in theory be reloadable. Assuming you can get the brass. My idiot neighbor bought a sig cross over 2 years ago and he has exactly 3 loaded rounds of ammo left out of the 2 boxes he was allowed to purchase with the rifle and zero access to dies. Needless to say that barrel is coming off soon and will be chambered in a cartridge that isn't a solution looking for a problem.
Just make sure you have your affairs in line before that bolt turns your face into a giant bloody donut.