Its all about timing, dont look at the animation of changing to detanator. If you time it right you can usually det the c4 before it hits teh ground.
What you do is throw the c4 while at the top of a jump so u launch it as far as you can.
Then wait maybe 1/4 of second and click right mouse button then wait another 1/4of second and blow it.
In the 1/2 of a second it takes to detanate you should be jumping away from the direction of where you threw the c4.