Polymeric-based ammunition cartridge casing with improved geometry

A polymer-based ammunition cartridge casing comprising:

• a casing body having a proximal end, a distal end and a longitudinal cylindrical wall extending between the proximal end and the distal end and enveloping a hollow interior of the casing body, wherein the longitudinal cylindrical wall of the casing body comprises:
• a first longitudinal wall portion which coincides with the proximal end of the casing body and is shaped to connect to a casing base, and further shaped such that when the casing base is connected, at least most of an outer surface of the casing base remains exposed;
• a second longitudinal wall portion connected at its proximal end to a distal end of the first longitudinal wall portion,
• wherein a minimal inner diameter of the first longitudinal wall portion is smaller than an inner diameter of the proximal end of the second longitudinal wall portion, and
• wherein the outer diameter of the first longitudinal wall portion is smaller than an outer diameter of the second longitudinal wall portion,
• wherein the ratio of (i) the minimal inner diameter of first longitudinal wall portion to (ii) the inner diameter of proximal end of the second longitudinal wall portion ranges between 0.90 and 0.97.