My days of competitive shooting are long gone. I lived through the Marine Corps transition to the mouse gun at Quantico. A good off hand position is established with a natural point of aim when you rely upon the geometry of your structure to provide a solid platform to recover from recoil without muscling the rifle. When mounting the rifle, you do not want your strong side arm wound up like Popeye when he's throwing a punch. You need a natural position. I shot the M14 with a spot weld with my forearm support straight under the stock directly ahead of the mag box. Having a high strong arm elbow gave me a natural pocket, allowed proper placement of my grip upon the stock wrist, allowed the stock to properly align with my face for a solid weld, and allowed a solid pull into my shoulder while maintining proper trigger control. If I attempted to raise my elbow, either too high or too low, from this natural position, I would bind and my solid platform would then break down.
Making the transition to the mouse gun required a change to to my natural shooting position due to the change in design and ergonomics of the M16. With the M16, my grip placement is changed and I shoot this rifle with a cheek weld vs a spot weld. As a result, my geometry requires that I adjust my position so that I do not bind/wind up like Poypeye.
Same thing can be said for different designs in hunting rifles and shotguns. I spend a ton of time hunting game birds with shotguns. The techniques used to swing and mount a shotgun to hit fast moving birds is critical to success and is much different than shooting either a M14 or a M16 off hand. There is very little in common in the mechanics to execute a well aimed shot. If you mounted an M14 like a shotgun, you'd never score very high, and if you mounted a shotgun like an M14, you'd hit few pheasants. One could say the same thing when looking at a heavy recoiling big bore designed for hunting dangerous game. The ergonomics of the rifle or shotgun plays a big part in how you apply your natural shooting position. It is not a one size fits all between all marksmen, and it's not a one size fits all between different disciplines of weaponry and shooting styles.
edit to add :
One could even say that how you would properly mount an M16 for CQB so that you could be most effective at hitting targets on the move, would be a completely different technique in how you would mount the same rifle to shoot off hand in service rifle competition to clean the target with max X hits. Both would look different, and neither would work well if the techniques were flip flopped.
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