So who uses one and how does it perform?
To be honest, it's CRAP.
The 270 WFC or 270 Winchester, is a much better cartridge.
The .270 Win. shoots with 17.5% greater velocity and has up to 11% more energy than the .280 rem. given certain loadings and ballistic contexts. The 270 was also used by famous people like Jack O'Connor, who didn't do much with the 280.
Jim Carmichael liked the 280 to some extent, but he may have been told to like it by powers that may potentially be, if it's what was said by someone?
The 270 Winchester, with the right bullets, is also more benchrest accurate and has greater angular momentum propensity and drive on animals, especially with the latest bullets that are not available in the 280 due to factory crap loads.
In all, with what was said previously, the best of all worlds resides with the 270 Winchester and not with the 280 win. which was called,
"the ...280 rem...often an also ran cartridge with poor ballistics and fading fast against the resurgence of the almightly 270 Winchester. Day in and day out, I'd rather have the hard hitting power and flat trajectory of a 270 Win. in my hands when a trophy Mule Deer appears at 300+ yards".
