Well, use whatever works for you tbh - my girlfriend gets amazing games in hardcore, and she uses nothing but the peacekeeper.
I would say that Nuketown is somewhat of an exception being a ridiculously small map. I normally will quit the lobby if it comes up, but if I am playing with the missus, I'll focus on anchoring our spawn, and making sure it doesn't flip (by camping HARD with the SVU lol) and she can run around in their spawn getting mega kills and stuff. I still think you'd probably do just as well with the FAL if you were accurate enough, that thing is hilarious in HC.
I find that most encounters on usual maps are actually at a reasonable range. For example, Standoff, Grind, Hijacked, Raid, all very common and popular maps have some excellent sniping positions.
The thing is, if you want to run and gun, the B23R is exceptionally good for that as well in my experience. I often get most of my kills with the pistol, but the SVU allows me to take advantage of getting into their spawn, or dominating a sightline for a while if spawns are flipping around me.
PSN: Toastie88 | XBL: ARGH ZUBATS | Steam: webbc99 Playing: MH3U, Call of Duty: Black Ops 2, World of Warcraft
The Type 25 is garbage in Core, but in Hardcore, it's beast. The faster movement speed makes you more agile, the higher rate of fire is great for hip firing, and the good irons mean you don't need a sight. If you are a run and gun type, this is your weapon of choice for Hardcore.