A few years back a pretty good shooter told=d me to shoot all my long guns from the 22LR ?Olympic? position. I started shooting trap that way and my scores edged up a bit. I started shooting multi-target sporting clays like that and my scores edged up a bit. M1 Garand and AR worked also. I am not sure it is the fastes way to shoot, but the consistency in method seems to make up for any faults in the posture.
IDK if it would work well for a super magnum or the ?57 T-rex? though.