Automatic

Automatic weapons tend to have weird dice amounts like d3's and d5's. This also extends loosly to shotguns, but looking at the 12.7mm Rifle from Science shows the following numbers:

12.7mm Rifle, 2d4 Auto.

When an automatic makes an attack roll, the person firing can choose to 'split' the dice. In this case the 2d4 can instead target two individuals each for 1d4+Half of Perception/Wisdom modifier (Rounded up). The attack roll is made as normal, but it is compared to each targets AC to confirm a hit. If the weapon has a +Damage Modifier, you choose which target to apply the damage to. It does not apply to every target.
In addition, some Automatic features increase the number of Strikes and Ammo Consumption so keep this in mind. For a truly powerful Automatic build, see Concentrated Fire As every attack made against the same target. (Aka each of these 2d4) will improve your damage/accuracy modifier accordingly.