Well stated. I've used this method except with the grenade intact. Were you there?FWIW...grenade triggers make great trip wire warning devices....they use a spring loaded device that strikes a percussion cap (easily replaced with shotgun shell primers)...just set up a trip line and when the primer goes off whomever hits the trip line think they are getting fired on...!
look for the grenade triggers at gun shows etc...they are usually a few bucks...primers are at a premium but worth the fun...