The work you all doing working with water is to be commended but surely is a lot of work.
Been there and done that a couple of years ago for similar bullet testing.
The media container was about 20 feet from the muzzle and beyond the chrono.
The media was contained in a very forgiving frame about 12" X 18". Only one bullet went beyond the 18" and didn't penetrate the 3/4" plywood backer. That bullet did not open in the slightest, only bent a bit.
I 'discovered' a peat moss type material out of canada that is processed for soaking up oil spills. I soaks water very well and has me feeling that it is much better and easier to use than water.
It takes a bit of a 'feel' to get the mix right to approximate flesh isn't too difficult.
Its reusable and easy to handle though when fully wetted it weighs like water.
I just set a garbage bag of the wetted stuff inside the frame which is inside a 25 gal barrel and go to shooting.
The bullet entrance is through a section cut from the thinnish cheapest plastic waste basket you can find.
Similar sections of the same waste basket are inserted every so many inches in the media to a) make it easier to find the bullet and b) to determine the uniformity of passage (straight, curved, tumbling, fragmenting, etc.) The barrier penetrations tell a tale.
Slide the plastic barrier out. If there's no hole the bullet didn't make it that far.
Without the barriers retrieving the bullet is pretty much like giving a constipated horse a rectal.