I don't know about other brands but necking down 6.5 ADG brass to .257 the .284 bushing or one a thou. +/- right around that size is what many are using. I just necked down a bunch of ADG 6.5 SAUM brass for a 25 SAUM build I having coming up and using a .284 bushing got me right around 2.5 thou neck tension with Hornady 134's.