99 x 284 in 284 should be looked at like a fast 7-08 for load info. You don't really have the magazine length to take advantage of long heavy 284 bullets,
My B.I.L. has taken a truck load of deer with his fast 7-08 + 120g (zippity-do-dah!). He now has a custom 99 x 7-08 that also likes the 120g Center target is two different three-shot groups at 100 yds (140g and 120g) that were shot to the same aim point. Last target is 200yds