What I've done with snipe chasing (when I do it, I usually stay in-base) is to catch up with the capper, and slowly chiselling down his health with the CG (I play sniper class instead of hornet or Rooster) and once the capper's health is low enough to be taken out with one LR shot, I stop, take a deep breath and zap him. There are two big downsides to this method, mainly, you lose all momentum, so if you miss with that one shot, you don't get a good chance at another, and secondly, it helps to have other chasers, partly for if you miss, and partly so that there's somebody to continue on and return the flag faster than the stationary sniper would be able to do.
Also, 7Fissurez, the old sniper rifle was a lot like the Spartan Laser from Halo, with a charge up followed by an instant kill. I don't know which came first, so I'm just going to point out that there's a gun in a VERY popular FPS with an incredibly similar mechanic. The largest difference between the Spartan Laser and the old LR is that the old LR had no ammunition restrictions. I know its harder to land a shot with the old LR than it is with the spartan laser, but would you like to be playing a more standard fps where there's some camping person with the old LR? Slower targets with a one-hit kill weapon with unlimited ammo is just ridiculous.