If think it's a little more than just in prefixes and suffixes.
The way I understand it, they have thousands of models of various gun parts (barrel, grip, sights, clips etc.) and then the software combines those to then create these over half a million unique weapons.
"Thousands upon thousands of barrels, grips, knife attachments, ammo, and clips are mixed and matched resulting in over 500,000 unique weapons."
-Game Informer
The way I understand it, they have thousands of models of various gun parts (barrel, grip, sights, clips etc.) and then the software combines those to then create these over half a million unique weapons.
"Thousands upon thousands of barrels, grips, knife attachments, ammo, and clips are mixed and matched resulting in over 500,000 unique weapons."
-Game Informer