Re: 6.5x284 Shooters
The 140 Amax and 142 SMK will remain stable through Mach 1 transition at 29.2 inHG 30F
My 6.5-06 would get the 140 Berger to a mile supersonic with a 28" barrel and Retumbo spitting them at 3150fps. If I slowed them down below 3100fps I got very erratic results at 1740yd, the bullet doesn't appear to remain stable through transition.
Depending on how long you 6.5-284 tube is and what the MV's are it will make it to a mile with the Berger, it just takes some pushing. Without risking over pressure or switching to a long barrel with Retumbo or H1000 then the 142 SMK or 140 Amax would be the 2 bullets that I'd suggest, having done it.
I've seen Tom Sarver shoot a 260 to 1650 and 1740 several times using the 142 Sierra and that certainly isn't getting there above Mach 1. You just need a bullet that makes it through the barrier point first or it's going to be extremely frustrating.