I bought a 284win a few years ago. The seller through in about 80 rounds of the factory 150 grn loads so I have not reloaded for it yet. I was planning on trying the 139/140?grn Hornaday Interlock bullets. The advice I saw was to stay at 140 or under due to the shorter neck. I think I would try some H4350,Varget, or something else in that comparable range.
I have an A-Bolt Micro-Medallion in 284 & it sure is a sweet gun in a great cartridge.