We have a fence around the back yard, and from inside the garage , looking out the back door to the corner of the yard is 25 yards. I have a jar lid that works pretty dandy nailed to that corner post, with a red thumb tack right in the middle. I set up the gun on a rest so that when looking down the bore (bolt removed) the jar lid fills the entire bore. (BTW I only do this with 22 cal rifles...22-250 and 22 hornet. Different bores would require different size lids.) Then, I adjust the scope so the cross hairs are centered on the thumb tack.
Usually, when I go to the range, the gun will hit within a couple of inches of the bullseye at 25 yards (where I always start to make sure the thing is even on the paper.)
The reason for doing this out of the garage would be obvious if you saw where we live. I would probably get jail time for fooling around out in plain sight with a high power gun with a scope.