Basically, for some reason that I cannot figure out by looking at the code, if you call either of the mbf21 projectile functions, A_MonsterProjectile or A_WeaponProjectile with a projectile that does not have the MISSILE flag set, ie for grenades and such, it will spawn with zero velocity applied to it. This is inconsistent with the behavior of the vanilla projectile code pointers, as they do apply velocity to non missile projectiles as can be seen with the Lee Killough grenade demo that came with mbf.
Basically, for some reason that I cannot figure out by looking at the code, if you call either of the mbf21 projectile functions, A_MonsterProjectile or A_WeaponProjectile with a projectile that does not have the MISSILE flag set, ie for grenades and such, it will spawn with zero velocity applied to it. This is inconsistent with the behavior of the vanilla projectile code pointers, as they do apply velocity to non missile projectiles as can be seen with the Lee Killough grenade demo that came with mbf.
EXAMPLES.ZIP
This bug is also present in dsda-doom and odamex, but it is not present in gzdoom.