Yeah but dividing stats is bad. if you are going for assault rifles, you will of course have str 7 but only because you need it for the feat, going above would be a waste no matter the reason. The thing is, you don't need melee when you use ARs, they are prime for close range and somewhat for mid range on semi.
If you are going for melee then you don't need ARs, you already got your up close and personal weapon in the form of a sledgehammer.
There just isn't much synergy between guns and melee. As far as I see synergies, they are guns with grenades, melee with grenades, melee with crossbows (for special bolts), melee with a hint of psi, psy with crossbows. those are the good synergies, you can do something different of course and i might be missing something here but for the most part, this is where synergy is.
It's mostly a case of how the game was developed. It was made with 3 main form of attacks. Melee, guns and psi. Those are the meat of combat. Crossbows and grenades, while good they don't hold on their own but make up for superb support combat skills... Whether intentional or not, this is how it is.
The problem of combining sledgehammers with ARs is. Your strenght (assuming the feat lowered burst penalty with more strenght) might be indeed reducing the penalties, but your perception on the other hand would be lowering your chances to hit since it would be somewhat low.
Really the way for this to work would be having an extra feat to reduce penalty for burst fire.