While not that new H4350 is temp stable and is about the perfect burn rate for mid range weight bullets.
H4831, another oldie, is used with 180s in the BR game by many shooters.
A slightly newer powder with similar burn rate to H4350 is RL-17. 17 will usually yield more velocity. Alliant's loading site is terrible and needs updating they list nothing for the 284 but a 110 gr bullet using RL-15 or RL-19. If you decide to try RL-17 the consensus is use mid range H4350 load data and work up.
Did a quick search and saw that IMR 8208 XBR is listed on Hodgdon's site for a 120 gr bullet and a few other lighter bullets. It is temperature insensitive.
One powder that has been around a while and is also temp stable is Varget. Hodgdon's website lists loads using it from 100 grs to 175. Heavier bullets will not be the fastest but if a particular powder is not available and you have varget, it will work.
Perhaps someone can discuss RL-16 which should work but again Alliant's site sucks. In this link Alliant mentions some loads using RL-16, of course not the 284, the closest is the 280 Rem.
https://alliantpowder.com/reloaders/Powder.aspx?powderid=41
