Late to the party on this one, but years ago when I built a 6X47 Rem (6-222 Rem Mag) I tried almost every bullet 80 grains and under in my rifle. I settled on the 70 grain Nosler BT as my go to bullet. I killed a few whitetail, pronghorn, and a lot of prairie dogs with that bullet. I'd love to test heavier bullets, but I'm limited due to a 1:14 twist barrel.
The 70 grain Sierra BK was a very accurate bullet. I often printed smaller groups with that bullet than I did with any other. However, my rifle seemed more sensitive to powder changes with that bullet. I often displayed pressure signs before I got close to the MV that I was able to achieve with the with the NBT.
IIRC, the Sierra was getting between 2700-2800 fps with the same charge of H335 that I was getting 3000 fps from the Nosler. Like any other small capacity case it doesn't take much of a powder change to spike pressures. I could have switched powders and maybe got velocity without pressure, but the rifle shot most everything under MOA with 70 grain bullets so I didn't stress about finding another load.
I did recently purchase 500 Norma Tip Strike 70 grain bullets to try from Raven Rocks moving sale. I was going to give the a go in my 6X45 that I normally use 85gr SGK bullets in. I may just try them in my 6X47 as well as I picked up 2K blems of the 85 grain SGK from Midway to run in my X45. I try to stick with 70 gr or heavier as it's the minimum for pronghorn in CO, but I only need a 55 grain bullet when hunting OK for whitetail.