Okay, an Autopistol stat line is S/-/X it can fire single shot or a burst of X rounds. A Stub Automatic is stat line is S/X/-. The Stub Automatic does more damage, so why would players choose an Autopistol? Or since I'm new to the game (and dumb) am I reading this wrong and the damage listed is for each round fired? Thanks for the help.

The damage is for each bullet. An autopistol can hit 6 times doing 1D10+2 with every hit. The stub automatic can hit 3 times doing 1D10+3 with every hit.

Also, full auto (S/-/X) gives +20 to hit and for every degree of success you hit with an additional bullet. If you need to roll under 45 and roll 35 you would hit with 2 bullets for example.

Semi auto (S/X/-) gives +10 to hit and for every second degree of success you hit with an additional bullet. If you need to roll under 45 and roll 25 you would hit with 2 bullets.

Notably, the damage is dealt for each bullet that actually hits . For people with a bad BS, it's usually best to get a gun with a full auto rating that is as low as possible - full auto so you get the +20 bonus, but low so you don't waste too many bullets that won't hit anyway.