Hi Ernie
JD will call it a maximized case Vs Improved.
6.5-270 blown out with very little taper, 60-degree shoulder, .250? neck. JD did a series of these based on the 06-cartridge family from 257 through 416 calibers.
The 270 Startline fired case holds 75.5 grains of water.

Here is a comparison picture with a standard 270 Win 150 BT (Left) and the 6.5-270 120TTSX (Right).


It?s fun to shoot, very little recoil, supper accurate!

D.