Someone else was complaining about this same thing--or was it you? Anyway, I think I'd try a different bullet, just to see if there is a difference. Say, 150-grain anything.
Try a different powder.
Check the bedding on your rifle.
In other words, you're gonna have to try some variables and see what changes. Load 10 rounds of 150 grain bullets and try at 100 and then at 200. Try ten loads of your 168-grains with a different powder and do the 100/200.
Damfino; good luck, Art