[Unclenick]

In resizing 308 Win brass, if all the brass went into neck thickness and none into neck length, going from 0.308" to 0.284" will increase wall thickness by 0.00107", and diameter by twice that. Most 308 Win cases run about 0.014" wall thickness. If you have that, increasing it to 0.01507" and seating a 0.284" bullet still won't exceed the SAAMI maximum for the 7mm-08 cartridge neck. So you may not need to turn anything off. That said, some 308 Win brass can be extra thick to start, so what you actually want to do is to try a few cases and seat a bullet and measure the OD of the neck over the top of the bullet. As long as it does not exceed SAAMI's limit of 0.3150" anywhere, you don't have to do anything about turning necks unless you want to for OCD reasons or to try to increase accuracy.