You guys who jokingly suggested swimming pools are on the right track.
Go to Walmart or Dollar General and get two or three of those $4.00, 24" long laundry baskets and two or three of the cheapest poly tarps you can find, about $3.00 each, or just one big one.
Line up the baskets on the picnic table in the back yard, line the baskets with the tarp or tarps and fill them with water. (At some point in this endeavor you'll most likely need to let your wife what's going on. I would suggest BEFORE you start shooting, which is when I should've told mine. )
(I no longer use jugs, just the baskets and tarps)
The rest is pretty self explanatory, shoot into the ends of the baskets and collect your bullets.
Some suggestions-
First and foremost, load the bullets you're testing down to expected impact velocity, and shoot from very close range. This serves two purposes; First it keeps us from having to shoot at the water baskets from from 50-100 yds. away and second, it allows more precise bullet placement. If one is careful to shoot through the holes in the baskets, they last much longer.
You can test multiple calibers at once, just have everything ready so you're not dawdling around while the water leaks out. My modus operandi is to load a cartridge to be tested and write the velocity on the case, shoot it, grab the bullet out of the basket and put it with the empty, like this-
....then quickly move to the next subject.
If two or three baskets aren't enough to contain your bullets, consider putting something behind the last one to stop them. It doesn't take much.
Bullets tend to tear holes in the tarps rather than cut them, so they leak more slowly than they would with full caliber holes. After you've punched a few holes in your tarp, it's simply a matter of gathering a little excess tarp in the basket and folding it over the holes. The pressure of the water does a pretty good job of holding the folds against the bullet holes and slowing the leaking.
When you're finished shooting, spread the tarps out to dry, then patch the holes with duct tape.
Water in a fairly open space such as these baskets yields easily, so I figure if a bullet will expand there, it will do so in just about any other medium such and flesh and organs.
I'm probably forgetting something, but maybe y'all get the idea.
35W