I agree. There isn't enough difference.
Also I comment how the AKM feels. I own a real AK (7.62x39) and the one in Sandstorm feels like a toy gun. There should be more visual recoil and gun shaking like there was in the previous game. In Sandstorm it's like the weapon's stock is bolted to your shoulder and there is too little backwards recoil. The gun sights should shake more when you shoot.