After the aftermath patch they completly changed how ALL attachments function.
Foregrips add spread - i believe thats in the description of foregrips when you highlight it in the menu
Flash suppressors always added spread, but now when you aim down the sights, it provides no negative effects. Only when hipfiring.
Silencers now REDUCE spread & recoil. Doesnt reduce as much recoil has F. Supp do, and it also adds bullet drop, and decreases bullet travel time. EXCEPT on the M417 sniper. It does NOTHING except take you off the map. No negative effects to bullets for some reason.
Laser Sights on some weapons FEEL like it decreases accuracy or adds recoil, though there is no stats to back that up. It just FEELS like it.
And more. Sometimes its better to run a weapon free of attachments rather to have any at all. I run the M4 stock or with just a silencer, and its amazing.
As for bullet velocity and stats, those can be found at here at Symthic.com. The charts are confusing as hell to read, and even their tutorials on how to read them are a bit complex because... well Battlefield is a very complex game.
If you have any questions about any weapon, chart, spread sheet or anything, let me know and i'll try to clarify.