My gas gun load development

[IALoder]

105, 108, and 109 I run them at 29.4 of lever. I think you will get the results you seek pushing them a little harder. But work your load up to those levels.

I was also using Hornady brass, that stuff is tough.

105 hybrids, 105 match burners, and 108 ELDM's have all dialed in between 29.2-29.6gr in my rifle.  I think that's a pretty standard loading spot for the 6 ARC with 105's and 108's.  Like Dino11 said, maybe you need to push them a little harder!