Hi Forestwalker ....
As has been said, effective range is that range with which you can do two things.
One is, can you put 10 out of 10 shots into a 6" pie plate at undisclosed yards. The pie plate which does not contain all your bullets is too far.
Second.. I would take a cardboard box side and paste a 6 " pie plate on the far side (whree you cannot see it) just behind a front stake. This is fun to do, and will also tell you how you manage effective range on a cardboard "deer".
Two. Know your trajectory. Shoot to 100 or 125 yards then shoot back to the bench. Check out your trajectory. It usually means you aim a little low at first, right on from 50 or 75 yards to 100 or 125, then half way up the back to 140 or 150 and top of the spine for 170 to 175 usually. Your effective range, shooting from your best "field" position might actually only be 75 to 100 yards, but you need to know your trajectory too.
Aloha..
