I have never used a .30-30 on anything larger than black bear. But I have killed several black bear with .30-30's, and witness even more (my bear hunting partners)...Enough that I went to 150's for everything I use a .30-30 for. I was unable to discern any difference in performance between 150-170 grain on everything from Coyote's to, Deer, to Black Bear. 150's get the job done just fine, and do it with a touch less recoil.
That said, there's absolutely nothing wrong with a 170 in a .30-30...they're very proven killers.
This is my experience also. I prefer the 170's for several small reasons.
Ken Waters wrote in at least two articles the 150 grain bullets put deer on the ground quicker.
