What I used to do was roll the rifle to the Rt slightly keeping the head in place cycle the bolt back to battery whilst rolling it back to the cheek weld everything lines up nicely as you pulling back with the left hand (Which also rolls the rifle) it is then just a case of opening the fingers of the Rt hand to grip the wrist of the butt easy peasy with practice can be used in all positions except the recumbent, and the trussed chicken (X legged and tucked up my italics)