are you talking about medium or small ones, and what did you shoot at?

medium MG has a really really high hit dispersion, but you theres an ideal ammo for any encounter - you just have to fit the correct one.

also, if your advanced robotics is already higher then lvl5 and your faction-weapon skill on the same level as your firearms skill, then your faction weapon will have more dps naturally.

on mechs that have a weapon bonus high EP will result in racial weapons becoming higher DPS, this is true. Firearms are tricky in that they have many more variables than just high DPS. You'll need to choose ammo types appropriately, sit at a much shorter range, and must rely on precision firing extension levels to maintain high hit rates.

Firearms really come into their own when used for a very specific purpose. For example, if you want to farm mobs resistant to your race's primary damage type, firearms often provide a better damage type spread. Another example is using Medium Autocannons on a blue mech in order to extend your maximum range (the optimal will still be shorter, but with the very large falloff bonuses you can still do some damage at a very long distance). Fitting the turret slots of a green bot with firearms also provides better DPS and lower fitting requirements than using the other races weapons.

Firearms are clearly not the "best" weapon. But they have a niche role. In my opinion they should not be your main focus on a character, but when used properly can provide many interesting options.

I used to love Firearms..  I intended to be the odd one that specialized in them,  however the harsh reality of them hits, and hits hard!

They are WAY too heavy!  like, twice the weight which, for pvp means that you sacrifice way too much speed.

You could use your imagination and come up with all sorts of colourfull situations where you might be able to convince yourself that 'speed doesnt really matter'  but no matter which way you look at it, eventually speed is king.

As with regard bonus's...

indeed there are no bots which directly offers a bonus to firearms.  However, if you understand the maths of the 'fall off' you should be acutely aware that the bigger your 'fall off range' the more damage you do at any given range - therefore the only bots that truly give a bonus to firearms are those which have a 'turret fall off bonus'