Capacity is the key to making brass processing simple regardless of how many steps you go through. The capacity of the Frankford, Rebel 17 and Thumler B are all based on rock tumblers that were repurposed or copied. They're suitable for reloaders that process small batches of brass at a time, but if you're shooting enough that you have to go through the whole process everytime you go to the range, then their capacity is not practical.
How many cases each can process at a time is a subject of various claims. Capacity is determined by the volume of the container and the torque of the motor to move it hours on end without overheating. The Thumlers B is rated for 15 pounds total and is said to hold up to 1.3 gallons volume. This is just under 5L. They also claim "250 30-30 cases." The Rebel 17 is rated for 17 pounds, holds about 6L volume and is claimed to process up to 4 pounds of brass, which is about 400 .357 Magnum cases. The FA tumbler has a maximum weight of 30 pounds, and is 7L in volume. They claim "1000 .223 cases," but it should be noted that load would not include stainless media. With stainless media, the capacity might only be half that or less. All of these tumblers are typically sold with 5 pounds of stainless media, which suggests their capacities are roughly equivalent.
If you have more than a couple thousand brass casings or process anywhere close to a thousand a month, these little rock-tumbler-based machines have insufficient capacity. This is especially true if you shoot a higher volume of a single cartridge type. With lower volumes of many cartridge types, you could use several of these small rock tumblers, but unless you want to process brass every time you go to the range or several times a month, a larger capacity is much more convenient.
I reload what I consider to be a modest volume. I only own about 1000 cases of my most frequently used cartridge and I only reload for two cartridges. I find the Rebel 17 I use has adequate capacity, but barely. I have to stay on top of brass-processing or it gets to be a lot of work cleaning multiple batches to catch up. If you own several thousand, certainly if you have ten thousand or more cases of one type, and you reload 1000 at a time or more, then these little rock tumblers would be a big waste of time.
I bought the small rotary rock tumbler and I'm going to use it. But I would recommend a person buy a few thousand more cases and one of those small electric cement mixers. Then, unless you're reloading 10's of thousands of rounds a year, you only have to process brass a few times a year, say 5000 cases at a time, and it's only one batch. If you get one of these rock tumblers and you're going to run 40 to 60 batches a year, that gets to be a waste of time. The cement mixers don't cost more and the extra brass is worth it.
