As Larry said get in the zone to lower heart rate. After months of practice I could do it in 30 seconds. Some people call it meditation I called it self hypnosis, you must be completely relaxed. This was fifty plus years ago and I found that it lowered my heart rate right at 50%. In my later years I can no longer get completely relaxed, before I get there I'm asleep. I have had to learn free recoil, nothing touches the rifle except my fore finger on the trigger and my thumb on the trigger guard. What ever you do or however you do it get rid of that heart jump,it spoils more scores than anything else.