Heavier as only for the weapon Assault Rifle part, or for armor too? I only bought the game shortly after a certain african warlord made a video of it, but to my understanding the tin man (practically Gorsky) AR build is of the oldest and maybe seen as straighforward builds. Or, instead of metal armor, you can use heavy leper serpent or sea wyvern leather armor. The tailoring craft does not require the strenght of the tin can (more than 6 for ARs or 7 for Full Auto feat).
Maybe you can get a use out of Gunslinger for initiative, and alternating burst fire of the main rifle with bullet time for the pistol, between reloads. That, because I assume this is a non psi build. In which case, you can start at will 3 for the dexterity investment required by pistols besides the perception as for the rest of guns. Kneecap shot would be a good slow to have, consider too that you will have the dexterity for quick tinkering against nasty crawlers.
You could think of putting points in constitution for thick skull because you can be susceptible to CC. Or not and prefer grenades to CC first. Some defense is to be considered since you'll get more of a Bullet Strap Belt than a doctor's pouch for medicines. Perhaps suppresive fire could help you deal with snipers, who are out of you reach, but I wouldn't rely on it. To such combination, I see a must a feat of increased perception at veteran levels. Maybe the use of googles and mushroom salads for that bonus effective skill. When not a metal helmet that makes you inmune to flashbangs.
I'll say, don't forget about mobility or contingencies when focusing on balancing two different types of weapon. Otherwise, one could be listing the many possibilities available, proven or to be tested.
