I have the same rifle. And I would think that its all down to shot placement. Now I am not doubting your hits. But I have seen deer shot just a small amount back of the lungs run for 100 yards.
I shot a deer once in the lungs with a roundball and got a complete pass through. The deer ran 30 yards into the thicket (of course) and when I found her there was a gross looking foam out of her mouth. I am sure that was because I shut the lungs down.
If they are running off, I would change bullet weight or bullet style. Maybe something heavier. But I have little experience with sabots and bullets for taking deer. Every time I hunt with sabots and my favorite bullet, I never see a deer. Walk out with a round ball and they are all around me.