I have 2, a 16" carbine and a 20" rifle. I have personally killed 33 deer and antelope with the 6.8. I have used the 100 Grain Remington bullets for 26 of the 33 kills. I used Barnes X bullets on 2 deer, and I used the Hornady 110 gr hollow points of 3 deer. I used one 130 grain Winchester Power Point on one deer. and I used two 110 grain Sierra Pro-Hunters on one deer and one antelope.
The Remington 100 grain bullets shoot just over MOA so they are accurate, but less so than many other bullets, but have been VERY good killers. Far better than most of the others.
I have only failed to get exits on 2 large mule deer, and no deer or antelope has gone more than about 15 feet when hit by one. Most have fallen at the shot. DRT
The Barnes X bullets are all they claim to be. Sub MOA and good wound channels with 100% penetration, but with one 2 kills I can't say I have a lot of info to pass on. They work but are quite expensive so practice is going to be a problem if you are not a wealthy man or woman.
The Hornady 110 Gr HP bullets were super accurate but that's all I can say good of them. Very erratic in their performance on deer and antelope. My friend Cas G. and I used them in out 6.8s for deer and antelope the year Hornady introduced them. Some broke up into fragments and some made pencil sized wounds. The largest Whitetail I have ever killed in my life was killed with one of these that hit the neck bones. Dropped it stone dead, but the wound was so small even after the hit on bone that it was tight on my pinky finger. Cas killed 4 deer too, and all his kills were unimpressive, with one being a pencil wound and 3 being blow-ups. We both went back to Remingtons and Barnes after that season.
I look at the Hornady #10 manual and these were discontinued. I am glad of it too. Not good for anything but paper.
As a side note, Hornady now makes a 120 gr SST which some of my customers say is a very good bullet, but I personally have no experience with them.
The one I killed with the Winchester 130 grain worked as well as anything I have shot. I have killed deer with that bullet from a 270 Winchester and I know exactly what it will do at 400-450 yards so I figured hunting whitetails and mule deer in the brush would give be the same results at closer ranges from my 6,8, and I was right. 135 yards to a nice big mule deer. One shot. Whop! Down deer, exit wound, and get out the pocket knife. These 130s can only be driver at about 2400 FPS from my 20" rifle, but so what? that's faster than I shoot 170 grain 30-30s and my 30-30 is just fine for hits on deer out to 200 yards. This 130 at 2400 FPS was just exactly what I expected it to be. Outstanding! Shot about 1.3 MOA form my rifle.
The Sierra 110 Pro Hunters are very accurate from my guns going well under MOA without much trouble. They kill well, but always shed their jackets after about 10" of penetration. I have killed one deer and one antelope with them, but I have 4 customers that use them in guns I made for them and all tell me the same thing. I have only 2 kills with them but I have seen several more (about 10) so I can speak about them with some real knowledge.
I do not know if I could trust them for heavier boned game, or thicker muscles, but so far they have done well. I might use something else for black bear. Deer and antelope fall quickly to them and hits are easy because of their great accuracy. They are also not very expensive.
I use the Remingtons in preference to them because of the better performance inside the game, but they shoot groups 1/2 the size of the Remingtons, so it's a trade off.
For open country where shots are going to be a bit longer, the Sierra may be a better option, but for hunting in the woods where striking velocities are higher and penetration may be impaired by bullet failure the Remingtons are probable better.
The best bullets offered today for the 6.8 SPC are probably those offered by Nosler. They are making a few for the 6.8 that look to be outstanding, but as of now I have yet to buy any or kill any game with them, but I will give Nosler credit for paying attention to our needs. These new bullets were designed "from the ground up" for the 6.8 SPC. I'd be willing to bet they will be great.