Great, ok. But better? Explain.
While the RSASS is a true semi-auto, it has more kick per shot. I haven't messed around with it a whole lot, but I've found that if you're camping with a sniper rifle a faster firing rifle isn't always the best thing, especially if you're trying to make up for the first shot you missed on. with the AS50 and it's slightly slower rate of fire you have more of a chance to reset your sights on where you want the bullet to go.
BTW, this is just all my opinion based on my way of sniping. I don't ever try to use a rifle as an assault rifle like most guys do on this game.
Edit: I only play hardcore too, but I've sniped someone in the head and not gotten a kill before even on HC.