Here something from 6br site
Loading for this cartridge can be relatively simple--or as complicated as you can make it. There is a wealth of knowledge about the round and some great loads have been worked out. Using Hodgdon H4350 or H4831sc with bearing-surface-sorted Sierra 142s will get you in the running. For the 139gr Scenars, our friend Fatboy sums it up this way: "For Lapua brass, [try] 47-49gr H4350 (Fed 210m), or 49-53gr H4831 (Rem 9.5), or 47-50gr N160 (Fed 210m). If one of these loads doesn't work for you, you are doing something wrong, or you need to switch to 142 SMKs. Each of these loads are proven winners by AMU shooters as well as Regional Prone and F-Class winners. Start low and work up, don't concern yourself with a specific MV. Go with accuracy, and clean often."
When long-range competitors first started shooting the 6.5-284, many pushed the cartridge to max velocities. However, it soon became clear that peak velocities did not produce the best match results. The general trend has been to back off loads to the 2950-3000 fps range with 142 SMKs. This seems to produce better accuracy in most guns, along with reduced throat wear. In selecting a velocity, most of our "experts" say to pick a load that delivers best accuracy with low ES and SD. What velocity that represents will depend on your gun and barrel. John Brewer runs his loads about 2950 fps, while Bill Shehane normally loads to about 3050 fps in an Ackleyized 6.5-284 case.