I use the m24, I'm so use to the bullet drop I get marksman headshots +280 with no hassle at all. It's just point and kill for me now, which it can be with all the recon primaries once you get good at each. Once your good at headshotting, magnum ammo goes out the window and so the need for a larger caliber doesn't come in.
And the LOLs from killing self-righteous GOL snipers who cant understand how you got them in one shot is great.
Hardcore damage boost not required. Headshots RULE