Balloons. I buy the normal bright-colored kid's party balloons.
1) Dirt-cheap, available anywhere.
2) Flexible - I can make them any size I want.
3) Easy to see if you hit at distance.
The downside is cleanup - you don't want rubber bits all over the range. They bounce around in the breeze depending how you mount them, but that can be a bonus - my shooting has improved from waiting for the wind to hold it steady, then squeezing the shot quickly.
Blow up ten balloons, five each of two different colors (one color for you, another for a buddy). Put pairs of them at various ranges. On "go!", you and a buddy have to range, dope, and dial each balloon, then pop it. We allow unlimited shots, but you only have 5 rounds with you - the extras are 20 yards back and you have to get one at a time if you need them.
Try that and tell me it's not the most fun you've had shooting a rifle in a long, long time. It's a total riot, and awesome practice too.
