The LifeTime, and TriggerDelay (grenade lifespan)
Try setting the gibimpulselimit to a value that lets it impact the ground and not detonate, yet fragile enough that when an actor steps on it it will explode.
You can change the firing velocity by... Changing the firing velocity:
Code:
AddAmmo = Round
InstanceName = Some Round
ParticleCount = 1
Particle = TDExplosive
CopyOf = Some Grenade
Shell = AEmitter
CopyOf = Some shell
FireVelocity = 100
ShellVelocity = 10
Separation = 5