you should be happy with 2500fps no matter what you twist a 115 with. IMR3031 is a very consistant and often overlooked powder.
27.5grs is a compressed load @2450fps out of my 6.8 and shoots 5 in an inch easily at 100 yds.
H322 is also a good choice and my go to load is 29.grs and a 110 Sierra @ 2670fps.
That was the good news, now here's the bad.
At 2670 fps and 300 yds you need 5 1/2 moa and at 500 you will need 14 moa or in internet terms that would be 6 ft of hold over with that same great shooting 100 yard zero.
Switching to a 90 gr hp unfortunately won't do any better at the same distances.
Probably the best way to describe the H322/110 Sierra is that at 215 yds it will weld into 1/2" steel plate impressively but at 360 yds it leaves dirty rat shot looking marks, nothing more.
I like my 6.8 a lot and and have learned to live with the good and the bad.
