Originally Posted by dontask
why not just taper a little bit at the top where you can feel it with your finger and thumb but still retain the cylindrical shape to be rolled?
While the round grenades rolled well, it was even easier to slide them. Rolling a cylinder requires a well aligned bowl putting the centre axis perpindicular to the rolling direction. In the end it turned out to be easier to skid the grenades to their destination rather than roll them. If you don't line up the axis quite right the grenade could roll to the side.
Putting a smaller diameter shoulder to provide a nubbin to register on isn't possible with the way the internals work.
As to foam covers, I really can't get into the legal issues of providing an accessory which obscures the warnings and limitations of liability markings. As nice as a foam cover might look it really provides little practical benifit. A thin cover would get cut and look scruffy pretty fast. A thick cover wouldn't fit into standard grenade pouches.