Shooting a mooving target at a great range is not the easiest thing to do, particulary if the guy is doing slalom and if you are stuck with a rifle that you don't like(fkn' Garand). You really need to put your sight a little more on left or on right and try to hit the body, the head is nearly impossible. You can also wait until he stops moves, but most of the time he will aim at you so you really need to shoot fast, especially if it's a DFL's or any great player
I think that the best rifle for practicing is the Lee Endfield No.4, with the "3 vertical bars" iron sight, this is the best rifle for shooting moving targets. The G43 have the same kind of sight, but with the Endfield is the rifle that I exceel the most and have the most intuitive sight IMO. With K98 I found it's easier to kill really far targets(desert), but harder while your target is on the move. You really need to find what is the best rifle for you then practice a lot with. Some rifles will be good for you, some will need more practice.
Now with 2.4, theres too much US maps in servers, so I'm stuck with the Garand that I hate so much and I still don't understand how to use it. I play almost only on the US side only to practice with the Garand, but God I hate that piece of sh*t. If I kill someone with(I really say if) I sprint to the dead corpse to get his K98, then if I'm not killed, K98 rampage starts. Last Monday on Eppeldorf I had 10kills in the round for 16 death, then at the last minute I got a K98 and got 7kills in 8 shots