I wouldn't characterize a 1700 yard shot as nothing, but the target is much larger than a human. However, if you want enough energy left to do any damage, you're going to be shooting either a .50 BMG or a .338 Lapua.
What you guys fail to understand is that a rocket booster is NOT armored. The entire structure has been pared down to minimize weight. The whole development effort is to find out where things can be "lightened" safely, and what things cannot. NONE of it is designed to withstand a bullet impact. This is a fragile mechanism, upon which one does not need to impact with massive kinetic energy to cause catastrophic damage, you just need to weaken something to the point where the high stresses of takeoff will start a chain reaction of breakage. So no, you do NOT need a 0.50BMG or Lapua to "take it down".