Back in the 1970s, when great bullets did not abound and bad ones did, I corresponded with a very knowledgeable gun writer named Bob Hagel, who told me that I should do my own testing to see which slugs would penetrate and hold together before I took them hunting.
The following target is based on what Hagel used and is made to tear apart weak bullets. In the Ballistic Buffalo, only the strong survive.
Making the Beast: In front I stick two thicknesses of worn-out truck inner tube (1), which you can get for free at any tire shop. Behind it goes a bundle of water-soaked newspapers (2), and behind that, an 11x14-inch piece of 1/2-inch plywood (3). Behind the plywood I place bound bundles of water-soaked newspaper (4) that total 2 feet thick, and behind that, if I'm testing an extremely tough bullet (usually it's not needed), more plywood. In the rear, I use a post (5) or tree stump to lean it all against.
In the Buff: With an orange aiming dot marked on the upper-left-hand quadrant of the tire, I fire a shot from 50 yards. Then, I go up to the buffalo and carefully start pulling the paper bundles apart to see how far the bullet has penetrated, taking note of the size and shape of the wound cavity and the depth of penetration. When I find the slug, I remove it with a pair of pliers because it is as hot as hell.
Weight Up: The slug goes into a handloader's scale. I divide the resulting measurement by the original weight of the bullet to find the percentage of weight it retained. Try this yourself, and you will know how far your bullet penetrated, how big a hole it made, and how well it survived the trip.