>>15747353
Forgot to add:
It all depends on the platform, the weapon, the shooter's limitations and the actual situation.
If the shooter is in the kneeling, the support leg is up, knee over the foot (uses calf muscle), other leg (dominant) knee is on the ground, heel under the butt (barely). This allows for rapid ascension and movement. The elbow (support arm) draped in front of the kneecap. Elbow on the knee can 'jolt' off of the top of the leg if not secure and doesn't feel good. The body naturally hunches, which makes it more comfortable, and tightens the body position. I refer to it as the pyramid because the strongest part of the pyramid is the base.
The standing position depends on the abilities/limits of the shooter, location, situation etc.
Arms tight inside, a forward grip could aid in positioning so one wouldn't have to go strraight arm or cup the mag well (which I prefer), buttstock up higher so the cheek has a natural location to set and not bend the neck (can be uncomfortable). Support arm, regardless where it is, pulls to the rear to lock the stock into the cup in the shoulder. Tighter the pull, less recoil felt.
Body position is dictated by situation, however, movement must be assumed and anticipated (you would have to move at some point). This means your position should be one that you can naturally move from and not have to adjust, them move. Half step movements with deliberate rolls of the feet to avoid the 'bounce' and muzzle slightly dropped for quick target acquisition.
Hope this helps.
Pew pew pew