It took about 400 rpm to arm the centrifugal arming fuze of the M406 HE grenade, reached after traveling through the rifled M79 barrel out to around 20 meters, [at which point the grenade had reached some 3,700 rpm] one reason M79 grenadiers were usually also given a .45 pistol in the event things got busy in closer than that. Fuzing on the HEDP round may be different, but the bulk of our work was done with the M406, and the XM585 white star cluster, the few WP rounds available being unreliable after exposure to wet monsoon season weather.
Once the M406 detonated, it popped up in the air like a *bouncing betty* charge, went off and spread 300 prefragmented notched-wire frags at 1,500 meters per second within a lethal radius of up to 5 meters- the frags were not very aerodynamic, but like the notched-wire frag of the M26 *lemon* frag hand grenade, sometimes struck head-on like a needle, other times spinning sideways to keyhole and tumble into the recipient. Nasty, and not the sort of thing to be spreading around in classrooms.
Believe it or not we used to pick up and hand carry 40mm HE rounds to a collection point and detonate the pile, some services EOD teams will NOT hand carry em and counter charges each round at great expense of resources. We'd snag em and carefully carry em and set em down very easily and then counter charge the pile and destroy......
My experience with M406 grenades was in the field, less formal than at an EOD shop *in the rear with the gear.* But the usual procedure was to very, very carefully slip the blade of an entrenching tool under the grenade body without touching it [you think cheese can be sliced thin!] then slowly pulling it away via a 200-meter length of parachute cord or bomb lanyard [550 cord] tied to a hole in the shovel handle. The little Canadian FIXOR binary shaped charges they use now for 40mm grenades, especially those of the HEDP flavor, or a much better arrangement, and also work nicely for UXO mortar rounds and mines.
