Erno86, having worn out 3.5 30 caliber magnum barrels and each one's had 60% of the rounds through them fired using a scope, I can clearly see the outside edges of the recicule twist as the round fires. Isn't very much, but it can be seen with 13+ pounds of rifle and scope after firing a 200 grain bullet out at 2950 fps.
That torque coupled with the reward recoil that causes the muzzle to rise all contribute and the whole rifle moving about a bit while the bullet's going down the barrel is what makes magnums harder to shoot accurately off the shoulder.
US Navy Distinguished Marksman Badge 153
Former US Navy & Palma Rifle Team Member
NRA High Power Master & Long Range High Master
NRA Smallbore Prone Master