I only play hardcore modes. I don't know why but its the same thing with COD.
Here was my progression to get the recon class done.
M24 > T88 > M95.
With those guns, I used the M1911, and that Body Armour you get, though I've changed to magnum ammo.
The key to almost power leveling it picking a spot and camping it out. If your not getting 200+ on marksman bonus on a headshot, move out farther. Look to see where everyone else snipes from on every level. Don't avoid them, but find a little more cover and stay near. Let them get picked off and you just try to see who shot them... You gotta be quick thought. Find the head, adjust for gravity(about 15*-20* correction), squeeze. Right when you get to your spot, you might even want to squeeze off a round to see how much you should correct.