I've been shooting airguns for the last sixty-five years, in national as well as international comps as well, and that's the very first time I've ever heard of anybody using water and or dish soap to wash air gun pellets of any kind. In fact, it's the very first time I've ever heard of ANY kind of pellet cleaning being carried out.
Since we spend a lot of time and money keeping that thin skirt in a circular shape, it must be plain that throwing them around en masse in a bottle of washing-up liquid - or anything else - is going to distort them so much that they will end up useless.
Concentrate of keeping the barrel clean instead. NO pull-throughs, not even cleaning rods, just the correct size felt pellets from your local good-quality airgun dealership. I shoot a couple through my barrels before any serious shooting starts, and a couple at the end - that's it. Some of my vintage airguns are pre-WW2, and are still like new inside.
tac