Rethinking 308 winchester

[Unclenick]

This can be done, but it will raise pressure substantially. That may be why he is mentioning slow powder, which helps mitigate the problem. But there are three other basic problems here. One is that erosion of the throat will be great from the forces involved in extruding the bullet from 7.85 mm to 7.00 mm, so I would expect a very short accuracy life from the barrel. At the very least, moly or hBN bullet coating should be done to provide sizing lubrication for the bullet. The second is that narrowing a bullet by 11% means it must be very perfectly centered on firing. Any slight misalignment could lead to a significant offset of the center of gravity of the formed bullet, making it inaccurate. The third item is that to avoid excess pressure, powder charges will have to be kept low enough to do the job safely. Lowering a charge means lower muzzle pressure, so muzzle velocity is likely to be compromised.