RicinYakima
High Steppes of Eastern Washington
Not trying to interrupt, but catching bullets has been going on for over 125 years. Water was eliminated early on because of its incompressibility. Even at relatively low rifle speeds of 1400 f/s with jacketed bullets they tend to mushroom. Julian Hatcher developed the vertical water trap for police forensics, but it only worked for low speed handguns. Lead revolver bullets had to have a reduced powder charge to prevent changing the rifling marks. Snow, with enough depth over 12 feet, works well, but most don't want to wait till spring time and mark bullets. So, as of now, oiled soft wood sawdust appears to be the best. Myself, I think one of the new plastics would be good, but I'm to old to go looking for it.