I guess the best way to explain it is the need to accurately range a target for field target comps. The kill zone varies in size and being a few clicks off because you don't know the exact range can cause you to split a pellet on the rim of the kill zone and not knock it down for a confirmed hit. It is especially bad when they put targets at say 13 yards or say 38 yards. These high power scopes have adjustable paralax that let you focus it like a 35MM camera. All you need to do is focus it on a known range and mark it so when it's in focus you know the range.
I sight in for 10 yards. At ten yards you can expect to see a kill zone not much bigger than your pellet, say 1/4". At 13 yards I am already having to click down elevation up to 12 clicks. If I don't range it properly and they have a 1/2 inch kill zone or 3/8 inch I might catch the edge and not drop the target. At 35 I am heading back up from the lowest point of 32 clicks down(we are talking 1/8MOA target scopes, not 1/4MOA) but if you can't range 38 yards correctly you will not be at the right setting on elevation and catch the edge of the kill zone and miss.
The targets we use are designed to drop with 3FPE. If you clip the edge of the hole it takes almost all of the energy out of the pellet and the target will not fall, and therefore a miss.
When I hunt, which is almost never, I back it down to 8 power.
