I like to stretch out the distance. I've got a 14" gong that we shoot at out to about 100 yds; sometimes further. After doing this for awhile, 25 yards is no longer the slightest problem for any handgun that I own, including my Jennings J-22. (POS by most standards).
The gong gives a very satisfying CLANGGGG when you hit it, and you don't have to walk back and forth to check your results.
It may not be very scientific, but you can pretty much compare how hard various cartridges and loads hit by the way the gong reacts. (I wouldn't want to get hit by any of them.)
So far I'm best with my Colt Woodsman, often shooting 80% at 100 yards.
On our Memorial Day Weekend camp out we have an elimination shoot-off. There is anywhere from 25 to 50 shooters at the start. Shooters step up to the line and get two shots (if needed) to ring the gong. Everyone who is successful gets another crack ten yards further back. Those who miss are out. We keep going, ten yards each time, and folks start dropping pretty fast about 50 or 60 yards out. (we're all amateurs with varying skill and equipment. All handguns, no scopes allowed). The contest is usually won at 100-120 yards, depending on the wind and such.
When it comes to informal and fun competition, this is the best we've come up with yet.