Working on designing the ammunition for a fantasy/sci-fi setting is hard. I ended up leaning towards a 15mm high velocity cartridge for a few reasons.

The main one being diversity.

15mm a bit smaller than a 20gauge shotgun, but what if I buffed up the propellant and projectiles? The most scary of this line of thought I tried to draw to full scale in my book and include a cut away of the ammunition.

The projectiles are modelled more along the lines of an old cannon shell like in WW2 tanks and warships.

The HE is modelled off the ‘Mine’ shells used in German WW2 aircraft for explosive cannon ammo.

The idea was simple. Make a this needs to die now bullet, that could hurt something like a dragon or equally large and dangerous creatures that have op magic powers. So the idea of a 750gr 15mm projectile moving at 1800-2000fps with an exploding core sounds very useful for this kinda situation ^.=.^;

The gun you can see is an AUTO-8 Browning (Auto-5) and is one of the guns I’m considering adapting to fit this setting as a survival or battle weapon dunno.

The KSG-12 is competing for this role in my head but the Auto-8 is simpler to draw.

Enjoy