Is he shooting a mosin 100yds at another mosin, that has an 8" steel plate rigged to the trigger, so when he hits that plate, it fires the 2nd mosin, which shoots 100yds at a 3rd mosin with an 8" plate rigged to the trigger, which repeats out to 1000yds?

For what its worth, I have no actual reference for whether this is legit or not.