Frag grenades won’t work because you can’t cook them forever, and once you pull one out you can’t switch to another weapon. But the semtex timer won’t start until you let go of it or die. So this is probably a technical glitch. This will be a suicide run, but when you die the semtex will drop and explode the javelin. If you don’t have the javelin pulled out, this won’t work because only your current weapon drops to the ground. If you have the danger-close perk enabled, the resulting explosion will be even larger. I wonder if using last stand with this would have any effect, such as kills from the afterlife, or assisted suicide points for the enemy.