Barrel & Grit field manual
How much rock fits each tumbler barrel?
Advertised capacity is the total loaded weight—not the weight of rough alone. Correct fill gives the barrel a steady cascading action.
Aim for the working fill zone
Most rotary barrels behave best around two-thirds to three-quarters full by volume. Too little material falls hard; too much slides without useful action.
Use several stone sizes
Small pieces and ceramic media fill gaps between larger rocks. A well-graded load carries abrasive into more contact points and reduces bruising.
Weigh the complete load
Rocks, media, water and grit all count toward the machine’s capacity. Do not treat a three-pound rating as permission to add three pounds of dry rock.