Funny you should mention this, I just pulled the last 180 .530 balls from my rock tumbler this morning, I have a Harbor Freight dual cylinder tumbler that I bought 10 years ago, each cylinder holds 3 lbs, I toss 90 530 in each and turn it on and walk away for 5 to 6 hours and done! you would be hard pressed to see any sprue marks and any seam lines are gone, they look like Speer store bought, tried the plate glass before this, worked OK , I'm just lazy and would rather be working on a rifle or a horn instead of rolling balls by hand. Now that's tumbling the balls with NO polishing medium in with them, just the balls rolling against each other!