Worker, now try shooting those loads at 200 and/or 300
Before you give up, you should really try some R#19 with standard Win primer.
Case capacity of the 6mm AI and the 6/284 are close. I have a friend that is shooting the 80g Sierra Blitz BT at 3800 fps out of a 26" barrel in a 6 AI, and You can duplicate or better his load with R#19, but he does have a 14 twist which does not spike pressures as fast as the faster twist barrels.
Your Barrel length is not stated in your post.