This is fine if one is processing sand and same size gravel. Rocks will jam up the works as they will fill up the trap rapidly
View attachment 1998736
There is several salt peter caves near me. One is flooded and we dove in and got the large hand drill bits but stirred the botton and up came methane gas and we retreated.. LolWhen I lived in Tennessee I did a lot of caving and saw quite a few confederate bat guano saltpeter mining workings from the civil war.