Of course it is! I am a bona-fide optimizer, so I have to consider the ideal situation at the same time I'm considering more useful solutions that merely suffice. It is a logical caveat to the topic to call out the proper art before turning to the shortcut
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For parts that can fit, it might be worth trying the lighter weight Harbor Freight resin abrasive media. I haven't tried, but I bet that stuff would run in a reloading tumbler at half full. I'm certain that the ceramic abrasive would be way too dense/heavy for the tumbler to cycle. Of course this limits you to tumbling metals that are compatible with the abrasive and finish, but it's something.
I know I've thought of the same thing. I'm certainly willing to try when I have a project worth doing it on. I think the size and weight constraints (the capacity of the tumbler) are the main hurdle, and the usefulness of lightweight media are limiting, but there is still a good range of stuff that might work out. Like you've stated, it's nice to use equipment you own rather than going out and spending money for more equipment to do the job.