What is the difference of these 3 guns?

M4 CQBR 35/60
M4 CQBR-AP 35/105
M4 CQBR- Dual Mag 35/140

I know the Dual Mag one has faster reload, and the difference of ammo, But I don't know the extra effect like Armor penetration and Wall Bang, stuff like that?
Btw, i find them surprising good !

Oh and the M4 CQBR Dual Mag AP, I guess it's the combine version of the last 2.