How do i get the "Dominoes" challenge on MW2?

I know how to do it but i cant find out what level to do it on or what to use.How do i get the "Dominoes" challenge on MW2?
Kill an enemy by setting off a chain reaction of explosivesHow do i get the "Dominoes" challenge on MW2?
You can use one man army to lay down a c4 and a claymore. Position the claymore so that it is triggered but won't kill the person who triggers it. Position the C4 so it is in the area of the claymores blast radius. They trigger the claymore, it triggers the C4... dominoes.



Also, throwing a stun grenade near a red barrel when someone is near it makes it explode and I think this counts.How do i get the "Dominoes" challenge on MW2?
you know those barrels up top on afghan? just shoot one bullet into those barrels and hope fer the best