From my experience, most people develop a flinch on the bench and never acquire it in the field. Try sitting up straight so your body can move with the recoil. Leaning way into the gun gives you a lot more punishment. Also use a recoil pad on your shoulder. I use a Past Magnum and find it helps a lot. At the range with a magnum, I often use a soft sandbag between the butt and my shoulder to distribute the recoil better. As stated above, a frim grip is important too. Whatever you do, don' t develop a flinch, as that can be hard to cure. Make each shot a surprise when it goes off.