Since I live in Israel, I lag a lot myself. My ways of hitting moving targets with lag are:
A. Use M203. It's just great. Even if you miss a bit you still kill. Learn to switch fast between the 40mm and the 5.56.
B. Rapid fire. Usually in short range but can also work medium range. Shoot a lot at the target until it drops. If you think it might hit you, take cover, reload, and try again.
C. If he didn't spot you, wait for him to stop. Basically the only way in long ranges unless you can snipe with a 40mm.
As for m203 vs HK 40mm, I much prefer the m203, because my prefered weapon is the M16 anyway, and taking m203 is less bulky and has a much much much faster switching than the HK 40mm.
A. Use M203. It's just great. Even if you miss a bit you still kill. Learn to switch fast between the 40mm and the 5.56.
B. Rapid fire. Usually in short range but can also work medium range. Shoot a lot at the target until it drops. If you think it might hit you, take cover, reload, and try again.
C. If he didn't spot you, wait for him to stop. Basically the only way in long ranges unless you can snipe with a 40mm.
As for m203 vs HK 40mm, I much prefer the m203, because my prefered weapon is the M16 anyway, and taking m203 is less bulky and has a much much much faster switching than the HK 40mm.