This is directly from TC 3-21.5 (count 2 of Right Shoulder).
On count two, move the right hand from the barrel and grasp the heel of the butt between the first two fingers with the thumb and forefinger touching at the first joint.
If you are Army (JROTC, ROTC,Army Cadets, Reserve, National Guard or Active Duty), then you must follow this guidance. Period. Here is what it looks like:
Picture courtesy US Army