I've been doing a bit of bullet recovery work in my rifle reloading with lead bullets in 30-30, .224 and 30-06 and once with my 45 acp.
First- what doesn't work. I took a thick walled 3.5 foot pipe and welded a flat plate on the bottom end. I filled it up with sand and fired into the pipe from above while standing on a creek bank. All I recovered were little lead balls about half the size of a pea. Next I filled up the pipe with water and fired a .45 acp round into the water (230 grain cast lead with 5.7 grains of W231 running about 800 ft/second). The bullet threw about a half gallon of water into my face and bottomed out on the bottom steel plate.
Next I fired a .308 jacketed soft point from a 30-30 at approximately 1800 ft/second. The good news is that the bullet mushroomed nicely and didn't hit bottom. The bad new is that the entire three gallons of water in the pipe was thrown over me and my gun. Time for a new plan.
Next up was water-soaked paperbooks from my local Salvation Army at $0.50 each. After soaking them for 48 hours they expand 50% more than their dry volume. I placed them in square plastic buckets, lined them up and fired 30-30, .224 and 30-06 cast lead rounds into them. They stop the bullets nicely at about the 16-24" depth and the bullets are easy to find and examine for retained weight and form. This seems to be the easiest way for me to recover bullets so far. Good luck.
best wishes- oldandslow