I'm currently developing loads for my 6ARC (3 different loads for 3 different 6ARC rifles, actually), but the one I am commenting about is my 20" AR specifically.
1) My daughter uses this rifle to hunt deer and I've had nothing but success with the 103gr ELDX. 4" holes on the exit sides. I've never recovered one actually.
2) This particular AR actually likes the lighter bullets better (it's a 1:7.5 twist) and I've gotten consistent sub MOA with 95 gr bullets. The Hornady 95gr. SST has been the best grouper so far. The 95gr. Berger Hybrid Hunter is also showing really good signs. Finally, one that surprised me is the 100gr. Hornady Interlock. It gave me some great groups I wasn't expecting.
3) All of these are loaded with CFE223 powder, but I'm moving onto extruded instead of ball powders. According to Gordon's Reloading Tool (GRT) I don't get 100% burn with CFE223, hence the experimenting.
4) I tried the 90 gr Hornady CX and had horrible groups. I've abandoned that bullet.