A number of years ago I was working in a fabrication shop and was able to collect some offcut materials with which to build what I call my test tube. One sticks the rifle muzzle into the top and wraps a rag around it, and holding the rifle upright and the rag tight, one fires it. The device captures the muzzle blast and the bullet/boolit and that's it. All that's left to do is open it up and recover the bullet/boolit for inspection.
For testing paper patch boolits I would place a cloth over the catch tube to capture the patch fragments.