A few points to note
-The reason why it appears to be faster when you aim at the ground is because its not directly fighting against the world gravity...
-Friction only affects objects when they are touching another physics object
-Elasticity only affects how high objects bounce when hitting the floor.
-Physics Iterations property will affect behavior like bouncing
you could also just add a timer that triggers after the first bounce...which then radically adjusts either
-the physics density for each grenade
-Linear damping -The rate the object slows down over time while moving ( would suggest this is better)
-turns off the physics after a certain amount of time or even better, triggers its "immovable" Property as long as you test for it being at rest on the Ground
so it doesn't appear as a glitch
also i assume the grenade is supposed to explode...Your video doesnt show this but normally a Grenade explodes either on contact or after a delay
Shouldn't either of these actions cancel out the constant bouncing due to the fact of the grenade destroyed?