Set up in front of a tree. Have some cover in front of you too. If you can't get any cover in front of you, you must remain completely still and ready to shoot. Also, even though you are dressed out in complete camo, make sure there isn't anything on you that stands out. Glasses, belt buckles, watches. Are there colors on the bottom of your boots? Is there anything that stands out on your gun? Either you are moving or something is giving you away. Or, try calling less when the turkey is within that range.