[quote=@Sophrus]
Actually, quick question. Could a FRAME dual wield autocannons? One in each hand?
[/quote]

Yup; if the weapon entry states it can be used in a single hand. In the case of the AFC-40/L, it can be: 

[quote]Mount: carried, one or two hands[/quote] 
Larger autocannons and heavier calibers may require two hands for stability. Of course, wielding two also requires you to have enough spare power/weight.
You can mix and match different types of weapons as well, if both are one-handed.