It's a good question, and one I have sought the answer to for a long time over countless hours of practising.
What I have found is that, on a good day, I can hold the cross hairs within the target's central mass easily enough, but the hard part is releasing the shot while doing so.
By that I mean I can easily pull the cross hairs off the target when releasing the shot.
I also use the moving rifle technique, where, on a bad day, I have to accept the mandatory wobble, and muscle the cross hairs onto the target. Then, for that fraction of a second, when the cross hairs move somewhere within the animal, and settle, the shot is quickly released.
This is, in my opinion, the more risky option, and I miss more with it, than the first.
Much better for me, is when my hold is steady enough, to maintain the cross hairs within the animal, and put all my concentration into trigger control by trying to disturb the sight picture the least I can, while releasing the shot.
Naturally the ergonomics of the rifle are crucial to helping me here.
The hand pressure on the pistol grip, placement of the trigger finger, position of the trigger lever itself, the shape and size of the palm swell, all are paramount in aiding steadiness, and hence comfort, and ultimately ease of shot release.
Of course it's not something that comes easly, or even quickly, but requires constant practise, and refining, and when it all comes together there is no greater thrill.
Max.
Auckland, NZ