Best round for hunting?

[6.8 KLR]

Do manufacturers post info about what velocity a bullet should be traveling to open effectively? I would think most of the solid copper bullets are not moving fast enough to open reliably at Grendel velocities at 300 to 400 yards. Are there bullets for reloading designed specifically for use with the Grendel?

The 100 grain Barnes TTSX that I load to about 2900 fps, opens up down to 1800 fps.(according to their website). At a velocity of 2900 fps at the muzzle, that bullet is still traveling at 2094 fps at 500 yds. So to answer your question, "will a solid copper bullet open up reliably at 300 to 400 yds ?". I would say ,yes....