unions

We do, yes.

.50 on the left, .22 LR on the right.

They flank cartridges that are in the "big game hunting/ standard soldier's rifle" range.

I'm not sure why you'd consider it large either, it fits trivially in the palm of your hand.

Are you maybe imagining that the whole cartridge would be fired? because it's only the very end bit that actually gets shot, the rest of it is just to hold gunpowder and the bullet in place inside the gun.
The actual bullet itself is about the size of a pea, i think.