Here's what LadyKate has to say on those tumblers- she's GOOD, BTW The site is here:
http://www.creagan.n...orks/index.html"Harbor Freight-like tumblers take up to 18 hours to mill most powders sufficiently. This number is based on milling 12 different charcoals using 75-15-10 and pre-ground chemicals.
The mill media was .50 caliber lead balls and the weight of balls was 2.5 lbs. 100-200 g of composition (it varied a bit depending on what I was doing) was milled each time. Test firings were taken at 6, 12, 18, and 24-hour intervals. The test firings were trough burns and launches of 1.5" 35 gram dog food shells.
Most powders stopped noticeably improving after 12 hours but some required 18 to get to potential. Generally speaking, the harder charcoals seemed to take longer to mix to potential.
Cautions are: Don't overload the tumbler - the closer you come to 3 lbs., the closer you come to destruction of the motor.
Get spare belts (4" x 1/8" O-Rings work) - I destroyed three in doing the above experiments.
Advantages are: It is a cheap way to start if you don't want to build anything. Lloyd's mill designs are so superior for larger batches that it is almost laughable - but that doesn't mean you can't get results with these tumblers. I still use them to do small jobs and they work fine. These cheap tumblers are definitely for small batches with about 2.5 lbs. max
load weight (100-200 grams of comp) - but they do work for that.
" LK