Hmmmmm....I was wondering if the pins would do damage to the case mouths. I suspect the speed at which the tumbler operates contributes to case mouth damage. The pins are so small, I would not expect them to have enough mass/inertia to ding the mouths. But, the other cases have enough mass/inertia and my bet would be on the cases doing the damage and not the pins. Another variable would be how much water is in the tumbler. The water will slow the movement of the cases as they tumble and hence reduce the chance of high velocity impacts.
If I were to wet tumble, it would be with .30-06 and .32-40 cases, the latter having very thin case walls at the mouth. Looking at the design in the two vids, I can see those interrupters he glued inside hitting case mouths and denting them. I think small plastic balls cut in half might be better. The balls inside Guinness beer might do the trick. And one sixpack should be enough.
It's a rainy day here. So, my mind tends to seek out diversions on such days. I was about to go to Horror Fright to price their rock tumber. I think what I'll do instead is just find my rubber tumbling drum and maybe do some brass at the lake. Need to find a way to turn it. Lathe runs off my little Honda generator and really don't want to run that for an hour. Maybe I can rig up my 1/2 drill to turn the drum. Pins will be the challenge, since I don't have any here and ordering adds a time delay. Maybe I'll cut up a 3 foot piece of 1/16" brazing rod. Or better yet, head over to the welding supply house and get a length of TIG wire to cut up. Lots of end polishing to be done in either case unless I tumble the pins with stones first.
What I like about the process is the internal cleaning, case and primer pockets.
I wonder if you could accomplish the same thing using fine gravel like they use in aquariums. Coarse sand might work as well. It would gradually become smoother with use. Initial use might be too abrasive. Hmmmmm.... damn rainy days.