The Side Mounted Scope on the 6.5 mm Carcano

[Bob Prudhomme]

Does the muzzle velocity of the smaller WC bullet decrease, and if so by how much? My high school physics tells me that the force on a bullet should be proportional to the surface area of the bullet exposed to the explosive gases. A .264 caliber bullet would have about 97% of the surface area of a .268 caliber bullet. Is the muzzle velocity 97% too?

I ask because the "magic bullet theory" has some pretty tight contraints on the velocity of the bullet. If it's too slow to begin with, you might fall outside the range of velocities that are medically required to produce the observed injuries.

Any ideas about how much muzzle velocity would differ for the smaller ammo?

I don't believe there would be very much difference in muzzle velocity due simply to the diametrical difference between the two bullets. If anything, the smaller bullet would have less drag due to decreased wind resistance, although a difference of .004" might make this difference in drag hard to measure.

As the undersized bullet would not completely fill the .268" grooves of the Carcano rifle, it is entirely possible that propellant gases could blow by the bullet as it travels through the barrel. This could have a tremendous effect on muzzle velocity.