While discussing numerous rifle, cartridge, and handloading subjects with a friend yesterday, he made the following statement: " I never thought much about the .338Win.Mag. until I read an article that said it had the same expansion ratio as the 7X57. I figured that was pretty good company, so I bought a .338 that week."
This led to me wondering about the expansion ratios of all the centerfire cartridges in common use. Has anyone ever seen a table listing this information? I'm curious and I bet others are, too. RS

I doubt that enough riflemen would be curious enough about this to make it worth anyone's while to compile such a table.

Calculating expansion ratios is simple enough � if you're interested enough, do 'em yourself.

case volume:
� Weigh several fired, unsized cases empty, then full of water to the mouths, to get the gross case capacity in grains of water.
� Subtract the weight of water displaced by the seated bullet to get the net case capacity in grains of water. A .224 bullet, for example, displaces 9.97 grains per inch of seating, a .308 bullet 18.84 grains, a .458 bullet 41.66 grains.
� Convert the net case capacity from grains of water to 0.? cubic inch (one cubic inch of water weighs, IIRC, 252.+ grains � about 8 lb/gal.)

bore volume:
In typical rifling, 75% of the circumference is grooves, 25% is lands. So here's how to calculate bore volume �
Add
� � land diameter x � land diameter x pi (3.141592654 � round it off wherever you like) x barrel length from base of bullet to muzzle x 0.25
plus
� � groove diameter x � groove diameter x pi) x barrel length from base of bullet to muzzle x 0.75

Then bore volume (x cubic inch[es]) is ? times the net volume of the powder cavity (y cubic inch).