TexasRick,
"The old Lee Navy is basically a 7x57mm with a semi-rim. Same capacity and shape."
Not hardly. The Lee Navy DOESN'T have a semi-rim. The rim is the same diameter as the body of the case. You're thinking of the .220 Swift, which originated by giving the Lee Navy case a larger rim, plus necking down AND shortening the neck. It has about five grains less powder room than the 7x57.
Specs for the Lee navy
Case type Semi-rimmed, bottleneck
Bullet diameter 0.236 in (6.0 mm)
Neck diameter .278 in (7.1 mm)
Shoulder diameter .402 in (10.2 mm)
Base diameter .445 in (11.3 mm)
Rim diameter .448 in (11.4 mm)
Case length 2.35 in (60 mm)
Overall length 3.11 in (79 mm)
Rifling twist 1:7�
Primer type Boxer large rifle
